A Web-based Sample Size Calculator for Reliability Studies

Planning a validation study of a questionnaire or measurement tool requires consideration for testing the validity and reliability aspects of the measurement tool. When it comes to the reliability aspect, a number of commonly used statistical coefficients such as Cronbach’s alpha, intraclass correlation, kappa and Pearson’s correlation coefficients would be considered to provide empirical evidence of the reliability of the tool during the validation process. To ensure that the reliability is accurately assessed, a researcher must consider the sample size requirement for the statistical analyses. In this article, I will introduce a newly developed web-based sample size calculator, which includes the ability to calculate the sample sizes of these four important coefficients. I will also show how to use the calculator for each of the coefficients.