Cronbach s Coefficient Alpha: A Meta-Analysis Study

Abstract

This study is to examine the meta-analysis results acquired from Cronbach alpha reliability coefficient being used in Hacettepe University Journal of Education. Within this context, 1222 items taking place in 43 issues which were published in Hacettepe University Journal of Education between 1986 and 2012 were examined and 354 measurement tools in total were discussed according to their inclusion criteria. In this study, r index was used in calculating influence quantity in correlational data for combining data while random influence model of Fisher z method was used in correlational data for combining influence quantities. It was benefited from SPSS 20 and MetaWin 2.0 packet programs for the analysis of data. It was found in this study that effect size mean is quite strong according to various moderator varieties of Cronbach alpha reliability coefficient. As a result of this study, it was determined that effect size mean of scale reliability prepared for measuring affective structure was greater than the scales prepared for measuring cognitive structures; effect size mean of reliability coefficient in adaptation studies was greater than the studies of applying and developing prepared scale. In addition to these results, it was observed that as the education levels of individuals within the sample and the number of items in scale increase, effect size mean of alpha reliability coefficient increases, too. On the other hand, it was determined that sample size and answer category number of option items did not have a direct influence on alpha coefficient. Afterwards, independent samples t test, one way ANOVA and Kruskal Wallis Test were conducted in order to find out whether the mean of Cronbach alpha acquired in line with the determined moderator variables varied according to groups. According to these analysis results, it was determined that structure of data collection tool, content of the sample, item and number of option had significant differences on Cronbach alpha coefficient. In addition to the variables within this study, different variables which are thought to affect reliability can be handled and the effects of these variables on reliability coefficient can be examined.