Calculation and Justification of Sample Size in Researches of Psychological Sciences: Application of G*Power Software

Document Type : Original Article

Authors

1 Assistant Professor, Department of psychology, Tarbiat Modares University, Tehran, Iran.

2 Professor of Psychology, Shahed University, Tehran, Iran.

Abstract

Appropriate sample size calculation, its justification, and power analysis are too 
difficult in psychological sciences. The process of sample size calculation and power 
analysis using statistical formulas, especially without any background is too difficult. 
The informativeness of research depends on this justification. The more collected 
data, the more informativeness according to its inferential goals. In this paper, basic 
concepts have been discussed and then, G*Power software was briefly introduced 
for sample size determinations and power analysis. Briefly, 3 practical examples of 
the sample size calculations using this software were finally introduced. This 
software supports sample size calculation and power analysis for various statistical 
methods including exact test, t-tests, F-tests, Chi-Square tests, and Z-tests, each of 
these family tests includes many statistical tests. This software is user-friendly and 
useful software for estimating sample size and power analysis in psychological 
science research. This paper provides insight for a psychological researcher and it 
will make the researcher able to apply this software to other statistical tests

Keywords

References

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11.927
Clinical Psychology and Personality
Volume 20, Issue 2 - Serial Number 39
February 2023
Pages 221-234

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