Restorative Dentistry and Endodontics

The Korean Academy of Conservative Dentistry (대한치과보존학회)
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An elaboration on sample size determination for correlations based on effect sizes and confidence interval width: a guide for researchers

  • Mohamad Adam Bujang (Clinical Research Centre, Sarawak General Hospital, Ministry of Health Malaysia)
  • Received : 2023.10.11
  • Accepted : 2024.01.04
  • Published : 2024.05.31
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Abstract

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.

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Acknowledgement

We thank the Director General Ministry of Health for permitting us to publish the paper.

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