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Realism and robustness require increased sample size when studying both sexes.

Szymon M Drobniak1,2, Malgorzata Lagisz1,3, Yefeng Yang1

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Researchers may need larger sample sizes when studying both sexes. A recent article overlooked that biological sexes often have unequal variances, a flawed assumption for sample size calculations.

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Area of Science:

  • Biostatistics
  • Sex Differences Research
  • Statistical Modeling

Background:

  • A recent publication suggested that researchers do not need to adjust sample sizes for studies including both male and female subjects.
  • This assertion was based on the assumption of equal variances between sexes.

Purpose of the Study:

  • To formally comment on the aforementioned article.
  • To highlight the unrealistic assumption of equal variances between biological sexes in statistical analyses.
  • To explain the implications of unequal variances for study sample size determination.

Main Methods:

  • Critical analysis of the assumptions in the referenced article.
  • Explanation of statistical variance and its relevance to sample size.
  • Discussion of the biological basis for potential variance differences between sexes.

Main Results:

  • The referenced study's conclusion is contingent upon the assumption of equal variances between sexes.
  • This assumption is statistically and biologically unrealistic.
  • Unequal variances necessitate careful consideration of sample size to ensure adequate statistical power for both sexes.

Conclusions:

  • The assumption of equal variances between sexes is not generally valid.
  • Researchers must consider potential differences in variance when planning studies involving both sexes.
  • Failure to account for unequal variances can lead to underpowered studies and inaccurate conclusions regarding sex-specific effects.