The article by Jaykaran Charan and N. D. Kantharia discusses the importance of calculating the appropriate sample size in animal studies to ensure the validity and efficiency of research. The authors highlight that an insufficient sample size can lead to missing significant differences, while an excessive sample size can result in unnecessary resource wastage and ethical issues. They review various methods for sample size calculation, emphasizing the use of power analysis as the most scientific and favored method. Power analysis requires knowledge of effect size, standard deviation, type 1 error, power, direction of effect, and statistical tests. The article also introduces a crude method based on the law of diminishing return, known as the "resource equation" method, which is useful when other methods are not feasible. The authors recommend using software like G Power for sample size calculations and suggest including a detailed justification of the sample size in research manuscripts. They provide formulas and examples for manual calculations and list several free online resources for sample size calculation.The article by Jaykaran Charan and N. D. Kantharia discusses the importance of calculating the appropriate sample size in animal studies to ensure the validity and efficiency of research. The authors highlight that an insufficient sample size can lead to missing significant differences, while an excessive sample size can result in unnecessary resource wastage and ethical issues. They review various methods for sample size calculation, emphasizing the use of power analysis as the most scientific and favored method. Power analysis requires knowledge of effect size, standard deviation, type 1 error, power, direction of effect, and statistical tests. The article also introduces a crude method based on the law of diminishing return, known as the "resource equation" method, which is useful when other methods are not feasible. The authors recommend using software like G Power for sample size calculations and suggest including a detailed justification of the sample size in research manuscripts. They provide formulas and examples for manual calculations and list several free online resources for sample size calculation.