Restorative Dentistry & Endodontics

Mohamad Adam Bujang

2 Articles

An elaboration on sample size determination for correlations based on effect sizes and confidence interval width: a guide for researchers: Mohamad Adam Bujang; Restor Dent Endod 2024;49(2):e21. Published online May 2, 2024; DOI: https://doi.org/10.5395/rde.2024.49.e21

Abstract PDF PubReader ePub: Objectives
This paper aims to serve as a useful guide for sample size determination for various correlation analyses that are based on effect sizes and confidence interval width.
Materials and Methods
Sample size determinations are calculated for Pearson’s correlation, Spearman’s rank correlation, and Kendall’s Tau-b correlation. Examples of sample size statements and their justification are also included.
Results
Using the same effect sizes, there are differences between the sample size determination of the 3 statistical tests. Based on an empirical calculation, a minimum sample size of 149 is usually adequate for performing both parametric and non-parametric correlation analysis to determine at least a moderate to an excellent degree of correlation with acceptable confidence interval width.
Conclusions
Determining data assumption(s) is one of the challenges to offering a valid technique to estimate the required sample size for correlation analyses. Sample size tables are provided and these will help researchers to estimate a minimum sample size requirement based on correlation analyses.

Sample size determination for conducting a pilot study to assess reliability of a questionnaire: Mohamad Adam Bujang, Evi Diana Omar, Diana Hui Ping Foo, Yoon Khee Hon; Restor Dent Endod 2024;49(1):e3. Published online January 10, 2024; DOI: https://doi.org/10.5395/rde.2024.49.e3

Abstract PDF PubReader ePub: This article is a narrative review that discusses the recommended sample size requirements to design a pilot study to assess the reliability of a questionnaire. A list of various sample size tables that are based on the kappa agreement test, intra-class correlation test and Cronbach’s alpha test has been compiled together. For all calculations, type I error (alpha) was set at a maximum value of 0.05, and power was set at a minimum value of 80.0%. For the kappa agreement test, intra-class correlation test, and Cronbach’s alpha test, the recommended minimum sample size requirement based on the ideal effect sizes shall be at least 15, 22, and 24 subjects respectively. By making allowances for a non-response rate of 20.0%, a minimum sample size of 30 respondents will be sufficient to assess the reliability of the questionnaire. The clear guideline of minimum sample size requirement for the pilot study to assess the reliability of a questionnaire is discussed and this will ease researchers in preparation for the pilot study. This study provides justification for a minimum requirement of a sample size of 30 respondents specifically to test the reliability of a questionnaire.

Author index