Journal of Postgraduate Medicine, Education and Research

Register      Login

VOLUME 56 , ISSUE 3 ( July-September, 2022 ) > List of Articles

STATISTICS CORNER

Statistics Corner: Comparing Two Unpaired Groups

Keywords : Independent t-test, Student's t-test, Unequal variance, t-test Unpaired t-test, Welch's t-test

Citation Information : Statistics Corner: Comparing Two Unpaired Groups. J Postgrad Med Edu Res 2022; 56 (3):145-148.

DOI: 10.5005/jp-journals-10028-1594

License: CC BY-NC 4.0

Published Online: 01-10-2022

Copyright Statement:  Copyright © 2022; The Author(s).


Abstract

Statistical analysis comparing two groups is most frequently reported in the literature; an unpaired t-test is popular to inform results from two independent groups. The t-test is parametric and makes certain assumptions about the data. Literature, however, has shown that the t-test is robust to statistical assumptions violation. Many researchers, therefore, do not test assumptions to apply t-test. The robustness property of the t-test has certain limitations. A researcher interested in reporting results using a t-test must know the following: • What are the assumptions for an unpaired t-test? • Are assumptions essential and need to be tested? • What is robustness in the context of statistical tests? • Are there any reporting standards to report t-test results?


PDF Share
  1. Lamb TJ, Graham AL, Petrie A. T testing the immune system. Immunity 2008;28(3):288–292. DOI: 10.1016/j.immuni.2008.02.003
  2. Delacre M, Lakens D, Leys C. Why psychologists should by default use Welch's t-test instead of student's t-test. Int Rev Soc Psychol 2017;30(1):92–101. DOI: 10.5334/irsp.82
  3. Weissgerber TL, Garcia-Valencia O, Garovic VD, et al. Why we need to report more than ‘data were analyzed by t-tests or ANOVA’. Elife 2018;7:e36163. DOI: 10.7554/eLife.36163
  4. Fox J. Using the R commander: a point-and-click interface for R. Chapman and Hall. J Stat Softw 2016;75:213. DOI: 10.18637/jss.v075.b03
  5. PGIMER, Chandigarh [Internet]. [cited 2022 Jun 13]. Available from: https://pgimer.edu.in/PGIMER_PORTAL/PGIMERPORTAL/home.jsp#
  6. Zhang Y, Shang L, Wang R, et al. Attitudes toward statistics in medical postgraduates: measuring, evaluating and monitoring. BMC Med Educ 2012;12(1):117. DOI: 10.1186/1472-6920-12-117
  7. Hannigan A, Hegarty AC, McGrath D. Attitudes towards statistics of graduate entry medical students: the role of prior learning experiences. BMC Med Educ 2014;14(1):70. DOI: 10.1186/1472-6920-14-70
  8. Zar JH. Biostatistical Analysis. Pearson Education India; 1999.
  9. The t tests | The BMJ [Internet]. The BMJ | The BMJ: leading general medical journal. Research. Education. Comment. 2020 [cited 2022 Jun 9]. Available from: https://www.bmj.com/about-bmj/resources-readers/publications/statistics-square-one/7-t-tests
  10. Zimmerman DW. Comparative power of student t test and Mann-Whitney U test for unequal sample sizes and variances. J Exp Educ 1987;55(3):171–174. DOI: 10.1080/00220973.1987.10806451
  11. Kishore K, Jaswal V. Statistics corner: data management in Rcmdr. J Postgrad Med Educ Res 2022;56(2):102–105. DOI: 10.5005/jp-journals-10028-1571
  12. Altman DG, Bland JM. Absence of evidence is not evidence of absence. BMJ 1995;311(7003):485. DOI: 10.1136/bmj.311.7003.485
PDF Share
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.