EXAMINING IMAGES OF SCIENTIFIC INQUIRY THROUGH THE LENS OF
TEACHER CLASSROOM ARGUMENTATION

This paper focuses on the methodology employed during an exploratory study
designed to examine scientific arguments constructed by secondary science
teachers during instruction of topics based on either experimental or historical
modes of inquiry. The analysis is unique in that it combines both Toulmin and
Walton’s analytic frameworks for argumentation and considers an entire
instructional unit as a complete argument. Four highly experienced high school
science teachers were observed daily during instructional units for both
experimental and historical science topics. Data sources include classroom
observations, field notes, reflective memos, classroom artifacts, a nature of
science survey, and teacher interviews. The analysis using Toulmin’s
argumentation pattern revealed a common trend toward a greater amount of
scientific data used to evidence knowledge claims in the historical science units.
The analysis using Walton’s presumptive reasoning revealed that, while some
presumptive reasoning schemes remained stable across the two units, others
revealed different patterns of use. Examination of the interview and survey data
revealed five specific factors mediating the arguments constructed by the
teachers: view of the nature of science, nature of the topic, teacher personal
factors, view of students, and pedagogical decisions. The combination of
Toulmin and Walton’s frameworks as well as the analysis on the level of the
instructional unit proved a useful tool in analyzing the teachers’ instruction.

Ron Gray, Oregon State University
Nam-Hwa Kang, Oregon State University

Introduction

The purpose of this paper is to highlight the methodology used in an exploratory
study designed to examine scientific arguments constructed by secondary science
teachers during instruction. The analysis considered an instructional unit one long
argument and focused on how arguments constructed by teachers differed based on the
mode of inquiry, either experimental or historical, underlying the topic. While the details
of the background and results of the study will be detailed elsewhere, summaries are
included here to aid in the analysis of the methodology. After a brief introduction to
argumentation analysis in science education, the methods of the study are presented in
detail with a focus on the analytic framework and procedures.

Argumentation in Science Education
Argumentation is a genre of scientific discourse that refers to the ways that
evidence is used in reasoning. Unmoored from its ties to formal logic, argumentation
theory was developed to describe how to explain everyday, or informal, argumentation in
terms of rhetorical and dialectical arguments. According to Toulmin (1958), an argument
is “a movement from accepted data, through a warrant, to a claim.” Toulmin’s model of
argumentation was considered the first to challenge the “truth” seeking role of formal

2
argumentation. Instead, Toulmin’s model focuses on the rhetorical elements of
argumentation and their justificatory functions (Osborne, Erduran & Simon, 2004).
In The Uses of Argument (1958), Toulmin proposes a model containing six
interrelated components for analyzing arguments (Figure 1):
1. Claim: An assertion put forward publicly for general acceptance.
2. Data: Facts or evidences which provide support for the claim.
3. Warrants: Statements which provide a link between data and a claim.
4. Backings: Generalizations making explicit the body of experience relied on to
establish the trustworthiness of the ways of arguing applied in any particular case.
5. Rebuttals: The extraordinary or exceptional circumstances that might undermine
the force of supporting arguments.
6. Qualifiers: Phrases that show the degree of reliance to be placed on the
conclusions, given the arguments available to support them.
According to Toulmin, a claim is the base for all arguments. Toulmin indicates that a
good argument needs to provide good justification for a claim, which can be achieved by
providing warrants or backings. This focus on the structure, as opposed to the content, of
the argument allows for an analysis of the differences in arguments among different
scientific disciplines as well as within different contexts (i.e. science and school science)
(Driver et al., 2000). For instance, the warrants and backings used to make claims are
shaped by the guiding conceptions and values of the field. This is due to the fact that in
science what counts as evidence and the theoretical assumptions driving the
interpretations of that evidence are socially agreed by the community.

Figure 1 Toulmin’s Argument Pattern (Toulmin, 1958)

Toulmin indicates that claims, data, warrants, and backings are the essential
components of practical (simple) arguments, while “qualifiers” and “rebuttals” may be
needed in more complex arguments. Toulmin’s argumentation model generated interest
Data Claim
Qualifier
Rebuttal
Warrant
Backing

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among researchers from many different areas including science education because of its
utility in differentiating quality of arguments reflecting reasoning behind them.
Analyses of arguments constructed in classrooms using Toulmin’s argument
framework have primarily examined how students provide warrants for claims, when
they do so, and on what basis (e.g., Jimenez-Aleixandre, Rodrigues, & Duschl, 2000;
Kelly, Druker, & Chen, 1998; Osborne, Erduran, & Simon, 2004). These studies have
provided a great deal of information about the form of student talk or writing in various
settings but have provided little information about how well students engage in argument
construction in terms of content quality. As a result, analytic methods that examine
argument quality solely from a structural perspective provide little or no information
about how students’ conceptual ideas about the subject matter influence how they
coordinate theory with evidence as they construct an argument in support of a particular
viewpoint (i.e. the content of the argument).
Another avenue has sought to focus on the logic and content of dialogue for the
analysis of argumentation discourse in science classrooms and the underlying
presumptions in the argument. Walton (1996) has identified 25 schemes of argument
which are commonly used in the construction of arguments in what he terms presumptive
reasoning. He defines presumptive reasoning as that reasoning which occurs during a
dialogue when a course of action must be taken and all the needed evidence is not
available. Argumentation schemes that focus on presumptive reasoning focus on the
evidence and premises a person uses and force the respondent to examine the premises
held by the other. They shift the burden of proof from the individual advancing the claim
to the respondent as, in essence, the argument is true until proved otherwise. Such
reasoning is rooted in the idea that “if the premises are true (or acceptable), then the
conclusion does not follow deductively or inductively, but only as a reasonable
presumption in given circumstances, subject to retraction if those circumstances should
change” (Walton, 1996, p. 13).
The use of presumptive reasoning can be employed as a framework to analyze
classroom arguments because it reflects quite well what typically happens in science
classrooms (Duschl & Osborne, 2002). It also complements the weakness of the Toulmin
model in that it focuses not on the structure, but the content of the argument. By using
these two frameworks for an analysis of a teacher’s argument, differences in terms of
both the structure and the content of the arguments can be examined and compared to our
understandings of the differences between arguments for experimental and historical
sciences.
Within the past two decades, science education researchers have conducted many
studies of argumentation in the classroom. The majority of these studies, however, have
involved the use of argumentation by students during inquiry investigations (e.g. Erduran,
Simon, & Osborne, 2004) or discussing socioscientific issues (e.g. Sadler & Donnelly,
2006). These studies have mainly used Toulmin’s argumentation pattern to assess the
quality of student arguments during activities designed to prompt scientific
argumentation in the classroom.
Relatively few studies have been conducted on argumentation by teachers
(Carlsen, 1997; Russell, 1983). These few studies focused on how teachers use authority
to control classroom discourse. In addition, analysis of teacher argumentation in the
classroom has not been used to examine the manner by which teachers present images of

4
scientific inquiry to their students or the factors that mediate those images. Thus, the
exploratory study partially detailed in this paper marks an initial step in a research
program to improve secondary science teachers’ instruction on the methods of scientific
inquiry. Specifically, the study asked three research questions:
1. What structural differences exist between scientific arguments constructed by
secondary science teachers for experimental and historical science topics?
2. What differences exist in terms of the types and/or frequency of presumptive
reasoning schemes in arguments constructed by secondary science teachers for
experimental and historical science topics?
3. What factors affect the arguments constructed by secondary science teachers?
Answering these questions presented unique analytical challenges resulting in a
combination of the Toulmin and Walton frameworks for argumentation as well as a shift
in the grain size of the arguments analyzed as compared to previous studies.
Participant Selection, Setting, and Data Collection

A general qualitative methodology was applied to this study in order to reach a
deeper understanding of possible differences between the arguments secondary science
teachers construct in the classroom for topics that rely on different modes of scientific
inquiry. The teacher participants in this study were selected by purposeful sampling with
no intention for generalization. In order to examine information-rich cases, teacher
participants were selected using a number of criteria. Participants who are highly
experienced (minimum of 8 years of experience) high school science teachers and highly
competent (additional academic and/or research experience) in their subject matter were
selected. It was also important that they teach both experimental and historical science
topics during the data collection period.
Among several different strategies of purposeful sampling, snowball (or chain)
sampling was used in this study. Snowball sampling involves contacting and recruiting
participants who fit the sampling criteria and then expanding the participant pool by
adding referrals for potential new participants, provided by the existing participants
(Glesne, 1999). The nature of this study required recruitment of secondary science
teachers as participants. In order to locate these teachers we began with knowledge of
teachers in the area to recruit the first participants. Further participants were recruited by
asking the initial participants to introduce or refer other individuals who fit the study’s
criteria. A total of four teachers were recruited as participants representing the most
highly qualified secondary science teachers in the district.
All participants have been assigned pseudonyms. The selection process resulted
in four high school science teachers being chosen for the study: Scott, Matt, Gabby, and
Robert. All four teachers were currently teaching science at one of two public high
schools within the same district in a mid-sized city in the Northwest. Scott and Matt
teach science at West High School whereas Gabby and Robert teach at East High School.
These participants were selected based on their willingness to participate and their
background in teaching and science.
Data collection took place in two large public schools in a mid-sized city in the
Northwestern United States. The two high schools are in a large, diverse district known
for serving a large range of socioeconomic backgrounds and a large migrant Hispanic
population. The study’s two high schools represent extremes within the district. We

5
observed three of the participants (Scott, Gabby, and Robert) during instructional units on
DNA and evolution. The fourth participant (Matt) was observed during units on
chemical bonding and the formation of the solar system. Class sizes ranged between 20
and 30 high school students.
Classroom observations, the primary data source, occurred in the participants’
classrooms during regular school hours. Participant surveys and interviews occurred in
this setting as well. Qualitative research methodologies utilize four basic types of data:
observations, interviews, documents, and audiovisual materials (Creswell, 2007). In this
study, all four of these types were collected through classroom observations, field notes,
reflective memos, classroom artifacts, a nature of science survey, and teacher interviews.
According to Patton (1990), observations of situations allow for greater understanding of
the complexities of a situation than simply interviewing participants. To absorb the
language, understand the nuances of meaning, appreciate the participants’ experiences,
understand the importance of what happened, and feel the intensity of situation, nothing
can substitute for “direct experience” (Patton, 1990, p. 262). The observations for this
study occurred during instruction on both experimental and historical science topics.
Field observations of the four classrooms occurred daily during the duration of the
chosen units which ranged one to three weeks per unit.
The objective for collecting observational data is to provide the reader an entrance
into and an understanding of the classroom situation by providing factual, accurate, and
thorough descriptions of the setting and the activities and perspectives of the participants
(Patton, 1990). During the classroom observations, a camera was setup to capture the
entire class. This allowed us to capture all whole-group interactions. As the data focused
primarily on the teachers’ dialogue, small group work was not recorded in detail. A
digital audio recorder was placed near or on the teacher as well as a backup measure.
The classroom observations were videotaped and transcribed verbatim.
As part of the field data, the field notes included “note taking” (Green & Dixon,
1999) in the form of thick descriptions of settings, activities, events, and classroom
discourse. These included student and teacher behaviors and interactions as well as
instructional methods. Thick, rich descriptions provided the foundations for analysis and
reporting (Patton, 1990). Reflective memos were also written immediately following
each observation. These included our feelings, interpretations, preconceptions, and
questions for subsequent interviews. These were meant to inform future directions for
investigation.
We conducted classroom observations for each lesson in both the experimental
and historical science instructional units of each teacher. This amounted to 57 individual
classroom observations, or roughly 85 hours, recorded and transcribed for subsequent
analysis over the course of the study. On three occurrences we were not able to conduct
the classroom observations. In these instances the participating teachers set up the video
recorders to ensure that data was not lost.
According to Patton (1990) interviews should be conducted to elicit the
meaningful description of the respondent’s life and opinions. Interviews are a Robert
source of experiential data about one’s beliefs, feelings, and activities. In this study we
conducted both pre- and post-instructional interviews with each of the four participating
teachers. Shorter informal interviews occurred often during the observational period to
elicit the participating teachers’ immediate reflections on the lesson.

6
The pre-instructional interview protocol used in this study was designed to elicit
reactions regarding the teachers’ opinions about their students, their role as a teacher, the
impact of their students on instruction, basic pedagogy, the goals of the two units under
study, and possible influences from the community that may impact instruction. These
foci of the interviews were drawn from the literature regarding teacher beliefs and
practice that report factors affecting instruction (Jones and Carter, 2007).
By contrast, the post-instructional interview protocol was designed to elicit their
reaction to their instruction in relation to their original goals and objectives as well as
their understanding of the scientific topics of the unit, the differences in methodologies
between the two topics, and their understanding of scientific inquiry. These questions
were specifically not included in the pre-instructional interviews to avoid influence on
their instruction. Interviews lasted between 45 and 90 minutes. All interviews were
audiotaped and transcribed verbatim.
Teacher understanding of different methodologies in science is part of the larger
construct of the nature of science. In order to assess the teacher participants’
understandings of the nature of science a brief open-ended survey instrument was
administered before the pre-instructional interviews. Lederman, Abd-El-Khalick, Bell,
and Schwartz’s (2002) Views of #ature of Science Questionnaire (VNOS-C) was used to
assess understanding of specific aspects of nature of science as highlighted in current
science education reform documents ([AAAS], 1990; [NRC], 1996). These include the
tentativeness, empirical nature, subjectivity, and social/cultural embededness of scientific
knowledge as well as observations and inferences, theories and laws, and the diversity of
scientific methods.

Data Analysis

Analytic Framework
Two analytic frameworks were used in this study, Toulmin’s (1958)
argumentation pattern and Walton’s (1996) schemes for presumptive reasoning.
Toulmin’s (1958) argumentation pattern describes argument construction primarily as a
process of using data, warrants and backings to convince others of the validity of a claim.
He suggests that the statements that constitute an argument can be categorized as claims,
data, warrants, backings, qualifiers and rebuttals. Accordingly, the strength of an
argument is a function of the presence or absence of the structural components. This
framework has been used widely and has been influential in studies of argumentation in
science education. In practice, Toulmin’s framework has mainly been used to show how
students provide warrants for claims, when they do so, and on what basis (e.g. Jimenez-
Aleixandre et al., 2000; Osborne et al., 2004). Although rare, it has been applied to
examine teacher argumentation (Carlsen, 1997; Russell, 1983).
Simon, Erduran and Osborne’s (2006) used Toulmin’s pattern to analyze
secondary school science teacher discourse before and after they participated in a
workshop about developing materials and strategies to support the teaching of
argumentation in science context. They indicated that using Toulmin’s pattern enabled
them to assess the quality of teacher arguments. In addition, using Toulmin’s pattern
offered teachers a language for talking about science and understanding the epistemic
nature of their own discipline. In a previous study, the same researchers worked on the

7
development of Toulmin’s pattern for analyzing science discourse (Erduran et al., 2004).
They indicated that the coding of whole classroom discussions with the pattern can yield
argument profiles which can act as indicators of improved performance throughout
implementation of the lesson. These argument profiles provide a tool for analyzing the
structure of teacher talk in the classroom.
Another influential analytical tool used to examine argumentation in science
education is Walton’s (1996) schemes for presumptive reasoning. He defines
presumptive reasoning as that reasoning which occurs during a dialogue when a course of
action must be taken and all the needed evidence is not available. While Toulmin’s
(1958) model emphasizes the structure of an argument, Walton’s schemes focus on the
content of an argument. Walton maintained that argumentation is grounded in burden of
proof, presumption, and plausibility. He categorized arguments in terms of a schema of
25 common forms of reasoning. Duschl (2007) selected 9 of these as particularly
relevant to the science education context in his study utilizing Walton’s schemes to
examine middle school students’ arguments. For example, a reference to an external
source of information, such as a person or text, would be categorized as an argument
from expert opinion. According to Duschl (2007), this scenario of reasoning based on
partial evidence reflects well what typically occurs in secondary science classrooms. Of
those 9, six schemes were chosen for their applicability to this study (Table 1).

Table 1: Adaptation of Walton’s Schemes
Argument from Definition
Analogy Used to argue from one case that is said to be
similar to another.
Causal Inference Infer a causal connection between two events.
Evidence to Hypothesis Includes a hypothesis capable of being tested.
Example Does not confirm a claim conclusively, it only
gives a small weight of presumption in favor of the
claim.
Expert Opinion Reference to an expert source (e.g. person, text,
etc.).
Sign References to spoken or written claims are used to
infer the existence of a property or event.

The purpose of this study was to examine both the structure and content of
teachers’ arguments constructed for experimental and historical science topics. A
combination of both Toulmin’s (1958) model and Walton’s (1996) schemes is necessary
for this purpose. The application of Toulmin’s framework allows for an analysis of the
structure of the teachers’ arguments constructed in the classroom based on classification
of teacher statements into predefined categories (e.g. claims, data, warrants, etc.). It is
not enough, however, to only assert the frequency of these categories as a measure of
teacher argumentation because the quality of the dialectical or rhetorical arguments will
depend on various “appeals to” types of evidence. Walton’s schemes of presumptive
reasoning allows for an examination of the quality of the content of the argument.
Together, these analytical tools allow for a qualitative analysis of the similarities and
differences between teacher arguments for experimental and historical sciences.

8
In terms of structure, historical arguments have been shown to integrate and
compare many disparate pieces of information on which the claim rests. The tight causal
links emphasized in experimental arguments require a smaller amount of information.
These differences are likely to be revealed as structural differences in Toulmin’s model.
For instance, in a historical argument one would expect an increase in the amount of data
used to support a claim as well as an increased frequency of warrants, backings, and
rebuttals as disparate pieces of information are compared and linked to the claim. The
content of the arguments, as revealed by Walton’s schemes, are likely to show significant
differences as well. For example, in an experimental argument one would expect an
emphasis on arguments from ‘causal inferences’ signifying an inferential leap, whereas
historical arguments should emphasize arguments from ‘evidence to hypothesis’ as
multiple pieces of evidence are linked to form a hypothesis. Therefore, this analytical
framework is likely to reveal qualitative differences in both the structure and content of
experimental and historical arguments.

Unit-Level Analysis
Data was collected and analyzed for this study at the level of the instructional
unit. Previous studies utilized both the Toulmin and Walton frameworks at the level of
small sections of discourse (e.g., Jimenez-Aleixandre, Rodriguez, & Duschl, 2000) or at
the level of an individual class session (e.g., Erduran et al., 2004). Analysis at the level
of the instructional unit was chosen for this study in order to more fully describe the
scientific claims of the teachers as they most commonly occurred over multiple class
sessions. For example, Figure 2 details Scott’s DNA unit. Over seven days, he detailed
six claims, although none were discussed in only one day. Claim #2, for instance, was
discussed over six days. Thus, the unit-level analysis provided the appropriate level of
analysis for the research questions posed.

Figure 2: Scott’s D#A Unit
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Claim #1
Claim #2
Claim #3
Claim #4
Claim #5
Claim #6

Analysis Procedures
A general qualitative approach to analysis was used in this study (Strauss &
Corbin, 1998) meaning that it was inductive and emergent from the multiple data sources
collected. Qualitative data analysis consists of three concurrent flows of activity: data
reduction, data display, and conclusion drawing/verification (Miles & Huberman, 1994).
Data reduction for this study included transcribing, selecting, simplifying, and
transforming the classroom observations, interview data, and collected documents.
After transcription, the first phase of data reduction was to “fracture” (Strauss,
1987, p. 29) the transcripts and rearrange them into categories that facilitated comparison.
This consisted of reviewing the classroom observation transcripts to select appropriate

9
areas of text in relation to the first two research questions. From these selections separate
claims were determined and the remaining selections were reorganized into the claim
categories. To examine the first research question relating to the structure of the
scientific arguments these claim categories were coded utilizing Toulmin’s (1958)
categories of claim, data, warrant, backing, qualifier, and rebuttal. To examine the
second research question regarding the content of the arguments, the claim categories
were coded using Walton’s (1996) schemes for presumptive reasoning (see Table 1).
These sets of data, both the structure and content analyses, were displayed in visual
matrices for comparison. Direct quotes and specific concepts are presented in the matrix
displays to organize, conclude and assemble the data to allow final conclusion drawing
(Miles & Huberman, 1994). This occurred for each of the experimental and historical
units for each of the four participating teachers. These were compared across participants
as well as across unit type (experimental and historical). See Appendices A and B for
examples of these matrices.
To answer the third research question regarding factors influencing the teachers’
arguments the interview transcriptions and nature of science surveys were examined. The
instruments were analyzed to create profiles of each participant. Participants’ responses
were coded for each of the aspects of the nature of science assessed. Although each
survey item focused on a certain aspect of the nature of science, we examined responses
across all items to ensure consistency. Individual aspects were coded as sophisticated,
intermediate, or beginning.
The interviews were examined to reveal possible factors influencing the creation
of the teachers’ arguments. Over multiple cycles, the interview transcript data was
organized and coded to reveal common factors related to the results of the structural and
presumptive reasoning analyses. Combined with the nature of science profiles, these
factors were matched with the results of the previous analyses in order to examine which
factors may have mediated the argumentation patterns found.

Trustworthiness
Member check, triangulation, and inter-rater reliability were the main tools for
ensuring the credibility of this study. Member checking, or having the participating
teachers and a colleague review the initial analyses, is a process “to make sure you are
representing them and their ideas accurately” (Glesne, 1999, p.32). In this study a
member checking strategy was employed during the interviews to ensure we correctly
understood what participants meant. We asked for clarifications when needed and
rephrased participants’ statements to confirm the meaning. This included their responses
to the nature of science survey. During the interviews, participants were given their
assessment and asked to explain and justify their responses. Follow-up questions were
asked as needed to most fully understand the participants’ understandings of the nature of
science. Member checks also occurred after the classroom observations and the initial
stages of analysis were complete.
Triangulation of data was established by using multiple data sources. It is
intended to add support for findings through several independent sources of data that
confirm it, or at least do not contradict it (Creswell, 2007). To be trustworthy, data
sources should be compiled from different methods and sources (Creswell, 2007). In this
study, for example, the arguments constructed by teachers were not only determined from

10
the classroom observation transcripts but were also verified using the interview data as
well as the classroom artifacts. This reduces the risk that our conclusions reflect only the
limitations of a specific source.
The third strategy that was employed to establish trustworthiness was inter-rater
reliability. Inter-rater can be described as “a process of exposing oneself to a
disinterested peer in a manner paralleling an analytic session and for the purpose of
exploring aspects of the inquiry that might otherwise remain only implicit within the
inquirer’s mind” (Lincoln & Guba, 1985, p. 308). According to Lincoln and Guba (1985)
the researcher’s peer should be someone who is a peer in every sense and one has a great
understanding of “substantive area of the inquiry and the methodological issues” (p.308).
The authors independently coded initial teacher arguments to ensure reliability.
Independent coding resulted in 92% reliability between the two researchers. The few
discrepancies that did exist resulted in further discussion about the definition of analogies
which were resolved and the data recoded.

Result Summary

While the main purpose of this paper is to highlight the methodology employed, a
brief summary of the findings is included. The purpose of the first research question was
to compare the structure of the arguments participating teachers’ constructed during
instructional units on experimental and historical science topics. For each teacher this
required first to identify the scientific arguments and then to code the teacher talk from
each of the two instructional units using Toulmin’s categories: claim, data, warrant,
backing, qualifier, and rebuttal. In the analysis, arguments that had data statements
considered scientific in nature were included. For example, Scott provided multiple data
statements as evidence of the claim that DNA is shaped like a double helix. One, that
Rosalind Franklin’s x-ray crystallography photograph provided Watson and Crick
evidence “to figure out the structure of DNA” (experimental observation), is scientific in
nature. By comparison, his statement that DNA is “just a ladder, a twisted ladder”
(experimental observation), an analogy, is not scientific in nature. The focus of the
analysis is a comparison between the manner in which scientific data is used and
warranted in the construction of arguments for the two different modes of scientific
inquiry.
By comparison, the participating teachers’ arguments constructed for historical
science topics involved slightly more scientific claims than those constructed for
experimental science topics. The number of scientific data, warrants, and backings,
however, was much higher. Thus, the overall structure of the arguments for these two
modes of scientific inquiry was markedly different. Specifically, a higher number of
scientific data were used to evidence scientific claims in the historical science units. The
pattern of increased scientific data used in the construction of scientific arguments and
the subsequent warranting and backing of that data is uniformly seen across the four
participants. This implies that the structural difference was more likely because of the
difference in modes of inquiry and less due to teaching styles.
The purpose of the second research question was to compare the presumptive
reasoning schemes participating teachers’ used when constructing arguments during
instructional units on experimental and historical science topics. Unlike the structural

11
analysis above, these included both scientific and non-scientific arguments (e.g.
analogies). Walton’s (1996) argumentation schemes for presumptive reasoning were
used for the analysis. Of the 25 original schemes, 6 were chosen for their applicability to
the data in this study (see Table 1). As compared to the previous analysis which showed
common trends in the structure of the participants’ arguments, the results of this analysis
were more individualized, although common trends were found.
The analysis of the three teachers’ arguments constructed during experiential and
historical science units using Walton’s schemes for presumptive reasoning revealed
interesting patterns. First, the use the ‘analogy’ scheme across all participants was much
greater during the experimental science unit. On the other hand, the use of the ‘causal
inference’ and ‘sign’ schemes remained relatively stable between the two units. In
contrast to these patterns common to the teachers, there were differences among the
teachers’ arguments as well. While the use of the ‘example’ scheme was much higher for
Scott and Robert during their historical science units, Matt showed the opposite trend
indicating that he relied more heavily on examples during his chemical bonding unit than
his unit on the formation of the solar system. Matt also stood out among the other
participants in his increased use of the ‘expert opinion’ scheme, a scheme rarely used by
the other participants. Lastly, Scott and Matt both utilized the ‘evidence to hypothesis’
scheme much more heavily during their historical science units whereas Robert relied on
it more during his experimental science unit. Taken together, these results indicate that in
some instances a clear trend can be seen among the teachers’ arguments for topics
employing different modes of inquiry. In others, however, individual differences may be
related to differences in teaching styles, understanding of the nature of science, or other
possible mediating factors.
The purpose of the third research question was to identify factors that mediate the
patterns revealed in the two previous analyses. Data from pre-instructional interviews,
post-instructional interviews, classroom observations, and the nature of science surveys
was examined and coded to identify possible factors relating to the patterns. Five factors
were revealed during the analysis: teacher views of the nature of science, the nature of the
topic, teacher personal factors, teacher views of students, and pedagogical decisions.
While these factors are examined independently in this analysis, in actuality they often
overlap as contributing factors.
Two patterns were consistent over all participants. In addition, the structural
analysis revealed a pattern of increased use of scientific data to evidence the scientific
claims made during the historical science units. The presumptive reasoning analysis
revealed a greatly increased use of the ‘analogy’ scheme in the experimental science
units. This analysis also revealed three patterns that were not consistent across all
participants. While Scott and Matt utilized the ‘evidence to hypothesis’ scheme heavily
during the historical science unit, Robert used this scheme sparingly. Scott and Robert
utilized the ‘example’ scheme far more in the historical science unit, whereas Matt used it
more during the experimental science unit. Finally, Matt utilized the ‘expert opinions’
scheme more heavily in both units in contrast to Scott and Robert’s sparse use of the
scheme. These five patterns seemed to be mediated by a combination of the five factors
described below.

Discussion and Conclusion

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This study marks the first attempt at using argumentation analysis at the level of
an instructional unit. Previously, the majority of studies have concentrated on the
analysis of argumentation at the level of particular segments of classroom discourse.
Erduran et al. (2004) extended this to include whole-classroom conversation in their
study of middle-level science teachers before and after an intervention on the teaching of
argumentation to students. The authors utilized Toulmin’s (1958) argumentation pattern
to create argument profiles which could be used as indicators of improved performance
across lessons. Consequently, their scheme moved the use of argumentation analysis to
the level where argumentation in entire lessons could be traced and examined in detail.
This study attempts to move the use of argumentation analysis one step further to
the level where an entire instructional unit can be examined in detail. This increase in the
level of analysis presents specific difficulties. Whereas an analysis of the argumentation
during a small segment of a class or even an entire class session tends to focus on one
claim, analysis of an entire instructional unit contains multiple claims with data, warrants,
backings, qualifiers, and rebuttals spread throughout multiple days. Pulling these
together into a coherent argument for analysis was challenging as they were often
regularly repeated and not always explicitly referenced back to the claim. Therefore a
decision had to be made as to whether a particular data statement, for instance, should be
included as data for a claim if it was not obviously linked to that claim for the students.
Another difficulty involved the pulling apart of the statements for each claim for the
presumptive reasoning analysis. Teachers would often mix these schemes together. For
example, a teacher might provide an analogy while simultaneously providing multiple
examples and signs. These separate schemes needed to be teased apart for analysis.
In terms of the analytic framework, we found Toulmin’s framework to be limited
in detail. For example, while the structural analysis showed that the teachers utilized
more scientific data during their historical science units, Walton’s framework provided
increased detail by breaking these data into ‘causal inference’ and ‘evidence to
hypothesis’ schemes. This revealed that a specific type of evidence, that which is
combined with other evidence to back up a claim, was more prevalent in the historical
science units whereas teachers used a similar amount of ‘causal inference’ schemes in
their experimental units. In other words, the analysis using Walton’s schemes provided
increased detail, particularly at the level of the instructional unit.
This conclusion is similar to Duschl’s (2007) conclusion about his study
involving the analysis of student discourse in a middle-level classroom. Duschl (2007)
analyzed his data using both Toulmin’s (1958) argumentation pattern and Walton’s
(1996) argumentation schemes for presumptive reasoning as well. He found that the use
of Walton’s schemes “more adequately fit the discourse structures (e.g., dialectical and
rhetorical) and reasoning sequences of the [data]” (p. 169). For Duschl, Toulmin’s
argumentation pattern uses too broadly defined categories to characterize arguments.
During argumentation, the students in his study would frequently make “appeals” to
specific positions such as an appeal to authority or to analogy. He found that the
examination of the content or focus of the “appeals” enabled an analysis that “gets closer
to the epistemic criteria being used to establish and justify the quality and strength of the
argument” (p. 164). Therefore, he switched to Walton’s schemes for presumptive
reasoning in his analysis as it provided, he felt, a more nuanced and detailed framework

13
for monitoring how students were employing evidence in the construction of
explanations.
In terms of implications for the science education research community the results
revealed the ability to utilize argumentation analysis to assess argumentation at the level
of the instructional unit. Therefore, a combination of Toulmin’s (1958) argumentation
pattern and Walton’s (1996) schemes for presumptive reasoning can be used by the
research community to examine other questions relating to teacher argumentation at that
level. In addition, the results show a link between a teachers’ understanding of the nature
of science and the diversity of methodologies employed by scientists to justify their
knowledge claims and their arguments constructed for their students. The results also
revealed specific factors mediating the construction of these arguments. This information
can be used to design further, more specific studies of secondary science teacher
argumentation.

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Lawrence Erlbaum.

15
APPENDIX A

Toulmin Analysis (Robert / Experimental)

Scientific Claim Scientific Data Warrant
#1: DNA is in all living things DNA extraction lab “Now we’re actually going to look at some
DNA today.”
#2: DNA is protected in the
nucleus.
Use of soap in DNA extraction lab “It breaks all that apart and that allows the
cytoplasm and stuff to come out. And then
you can break down the nuclear membrane
too.”
“In 1952, a woman did a very important thing. She
found in 1952 that by using x-ray diffraction that she
showed it looked kind of like this shape right there.
… Rosalind Franklin used in x-ray beam to figure
out the shape of that.”
“Now as soon as she did that it made it a lot
easier for 2 people that are credited with
figuring out the DNA structure.”
#3: DNA is shaped like a double
helix.
“Let me tell you about Chargaff’s rules. He found
that when he took a lot of DNA and sampled it, he
found that the % of adenine was the same as the % of
what? … [S] Thymine. … Whenever he tested he
found that they were always matching.”

#4: Messenger RNA is used to
send messages out of the nucleus.
“So 1960 is Brenner and this is what Brenner
discovered. He discovered that messenger RNA is
the way that the DNA gets its message out of the
nucleus.”

#5: Proteins are created from
DNA through transcription and
translation.

#6: DNA is the blueprint for all
cells.
“Oswald Avery … Some of the molecules they knew
is they knew RNA, proteins, fats, carbohydrates. He
would destroy those various ones to see if it still
worked and it always still worked even though he
destroyed those molecules.”
“that's where they discovered it was DNA.”

16
APPENIDX B

Walton Analysis (Robert / Experimental)

Scientific Claim Evidence Scheme
#1: DNA is in all living things DNA extraction lab: “Now we’re actually going to look at some DNA
today.”
Example
#2: DNA is protected in the nucleus. Use of soap in DNA extraction lab: “it breaks all that apart and that allows
the cytoplasm and stuff to come out. And then you can break down the
nuclear membrane too.”
Causal Inference
But when the construction’s going on it’s rainy and muddy, they’re digging
out there, and this is precious stuff, this plan right here. So when the
plumbers come, say some plumbers come on a rainy day to lay the pipes
before they pour the cement and say hey, we need to know where the pipes
go. Well, how do they figure that out? They have to have a plan. So do
you think the guy in the office there is going to say "oh, here's the page that
shows you that. While you take this out there in the rain in the mud and
figure it out." No, he’s not going to do that. This stuff’s precious. So it’s
help inside the nucleus in the office. What he does instead is he makes a
copy of this and he says "here's the plan, take it" and they go put on a piece
of wood out there and it gets all muddy and no big deal because it's just a
copy.
Analogy
Your DNA is protected. It stays inside the nucleus Sign
“In 1952, a woman did a very important thing. She found in 1952 that by
using x-ray diffraction that she showed it looked kind of like this shape right
there. … Rosalind Franklin used in x-ray beam to figure out the shape of
that.”
Evidence to
Hypothesis
“let me tell you about Chargaff’s rules. He found that when he took a lot of
DNA and sampled it, he found that the % of adenine was the same as the %
of what? … [S] Thymine. … Whenever he tested he found that they were
always matching.”
Evidence to
Hypothesis
Double helix. It looks like a ladder that has been twisted. Double helix. Analogy
So, this double helix thing is made up of two strands and they’re little
nitrogen bases here that are connecting…
Sign
#3: DNA is shaped like a double
helix.
For RNA, Uracil replaces thymine. So only U can hook up with the A.
There is no thymine. So on a test which you will get, and on the state test
Sign

17
too, whenever you see a U immediately you know that has to be strand of
the RNA.
They separate at their base pairs. And what makes them separate? It starts
with an E. [S] Enzymes. … Enzymes. Yes. It makes that thing unzip
Causal Inference
Remember that this thing is held together by chemical bonds and so you
have to keep in mind that there are enzymes that cells use to break those
chemical bonds. Those bonds are pretty weak. They are hydrogen bonds.
Causal Inference
These chemical things occur because there are chemical attractions. There
are bond things that make it want to come there.
Causal Inference
It's like a magnet that pulls it. Analogy
The mRNA slides along the ribosome. So this ribosome is actually an
organelle in them that causes these reactions to occur and it allows a things
to come and break things.
Another tRNA brings an amino acid that connects by a peptide bond. Not
going to make you memorize the kinds of bonds and stuff but it brings it in
and attaches by peptide bonds to the first amino acid. So we had one amino
acid now another one connected there. And look. All the other stuff goes
on or does other things or becomes defunct. The whole goal there was to
bring that amino acid.
Sign
“So 1960 is Brenner and this is what Brenner discovered. He discovered
that messenger RNA is the way that the DNA gets its message out of the
nucleus.”
Expert Opinion
That little strand of RNA and it's called messenger RNA, mRNA. It means
the messenger and it's going outside of the office out into the cruel world to
do work. But the precious DNA is stored in the nucleus and it never comes
out of there. It's staying in there so it can be protected, but the cell has to do
work. So all of the other workers come and they keep doing work and say
the plumber loses his plan or some kids are skipping at lunch and they go
take the plan and make paper airplanes. Does that mean we're not going to
have plumbing in the floor and the kids ten years later I run to say you know
they don't have bathrooms in that school because the plumber lost his plan?
No, they can just make another copy so another messenger RNA can go out
of the nucleus to go do work. Those are expendable. Those of the copies
that are meant to go do work.
Analogy
#4: Messenger RNA is used to send
messages out of the nucleus.
The mRNA leaves the nucleus and where does it go? To the cytoplasm. Sign