Study size

Abstract

In conclusion, this short article has addressed the issues surrounding the determination of appropriate study size. Only the sample size equations relating to the most common study types in the field of STI are presented. For more complex but common situations, the important issues to consider are highlighted. Many other sample size equations exist - for example, when the outcome is continuous, such as CD4 count, or more than two groups are compared. Several useful references are given in the further reading section. This article raises awareness of the need to perform studies of the correct size for the given purpose and informs the researcher in sexually transmitted infections of the particular points that they may need to consider.