Welch’s T-test: The Robust Default for Comparing Two Groups in Psychological Research

Keyword

Welch’s t-test; Student’s t-test; Mann-Whitney U test; Type I error; Heteroscedas-ticity; Robust statistics; Psychological research; Statistical inference; Beh-rens-Fisher problem; Variance inequality; Simulation studies; Statistical power; Artificial intelligence

References

Delacre, M., Lakens, D., & Leys, C. (2017). Why psychologists should by default use Welch's t-test instead of Student’s t-test. International Review of Social Psychology, 30(1), 92-101. https://doi.org/10.5334/irsp.82

Derrick, B., Toher, D., & White, P. (2016). Why Welch’s test is Type I error robust. The Quantitative Methods for Psychology, 12(1), 30-38. https://doi.org/10.20982/tqmp.12.1.p030

Haerpfer, C., Inglehart, R., Moreno, A., Wenzel, C., Kizilova, K., Diez-Medrano, J., Lagos, M., Norris, P., Ponarin, E., & Puranen, B. (Eds.). World Values Survey: Round seven-country-pooled datafile version 5.0. JD Systems Institute & WVSA Secretariat.

https://doi.org/10.14281/18241.20

McGee, R. W., & Benk, S. (Eds.). (2025a). The ethics of bribery, Vol. 2: Country studies. Springer.

McGee, R. W., & Benk, S. (2025b). Attitudes toward bribery in Russia. In R. W. McGee & S. Benk (Eds.), The ethics of bribery, Vol. 2: Country studies (pp. 101-119). Springer.

McGee, R. W., & Guadron, B. (2025). Attitudes toward bribery in Brazil. In R. W. McGee & S. Benk (Eds.), The ethics of bribery, Vol. 2: Country studies (pp. 191-210). Springer.

McGee, R. W., & Lee, B. (2025). Attitudes toward bribery in Sweden. In R. W. McGee & S. Benk (Eds.), The ethics of bribery, Vol. 2: Country studies (pp. 253-269). Springer.

McGee, R. W., & McCrowre, R. L. (2025). Attitudes toward bribery in Nigeria. In R. W. McGee & S. Benk (Eds.), The ethics of bribery, Vol. 2: Country studies (pp. 231-251). Springer.

McGee, R. W., & Zhou, J. (2025). Do all Protestants think the same way about bribery? A 55-country study. In R. W. McGee & S. Benk (Eds.), The ethics of bribery, Vol. 2: Country studies (pp. 561-566). Springer.

Phillips, L. T., & Lowery, B. S. (2015). The hard-knock life? Whites claim hardships in response to racial inequity. Journal of Experimental Social Psychology, 61, 12-18. https://doi.org/10.1016/j.jesp.2015.06.008

Ruxton, G. D. (2006). The unequal variance t-test is an underused alternative to Student’s t-test and the Mann-Whitney U test. Behav-ioral Ecology, 17(4), 688-690.

https://doi.org/10.1093/beheco/ark016

Welch, B. L. (1938). The significance of the difference between two means when the population variances are unequal. Biometrika, 29(3-4), 350-362. https://doi.org/10.2307/2332010

Welch, B. L. (1947). The generalization of ‘Student’s’ problem when several different population variances are involved. Biometrika, 34(1-2), 28-35. https://doi.org/10.2307/2332510

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