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Analysis of small sample size studies using nonparametric bootstrap test with pooled resampling method
Author(s) -
Dwivedi Alok Kumar,
Mallawaarachchi Indika,
Alvarado Luis A.
Publication year - 2017
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.7263
Subject(s) - nonparametric statistics , resampling , wilcoxon signed rank test , statistics , sample size determination , goldfeld–quandt test , parametric statistics , mathematics , statistical hypothesis testing , permutation (music) , type i and type ii errors , sign test , econometrics , test statistic , mann–whitney u test , z test , physics , acoustics
Experimental studies in biomedical research frequently pose analytical problems related to small sample size. In such studies, there are conflicting findings regarding the choice of parametric and nonparametric analysis, especially with non‐normal data. In such instances, some methodologists questioned the validity of parametric tests and suggested nonparametric tests. In contrast, other methodologists found nonparametric tests to be too conservative and less powerful and thus preferred using parametric tests. Some researchers have recommended using a bootstrap test; however, this method also has small sample size limitation. We used a pooled method in nonparametric bootstrap test that may overcome the problem related with small samples in hypothesis testing. The present study compared nonparametric bootstrap test with pooled resampling method corresponding to parametric, nonparametric, and permutation tests through extensive simulations under various conditions and using real data examples. The nonparametric pooled bootstrap t ‐test provided equal or greater power for comparing two means as compared with unpaired t ‐test, Welch t ‐test, Wilcoxon rank sum test, and permutation test while maintaining type I error probability for any conditions except for Cauchy and extreme variable lognormal distributions. In such cases, we suggest using an exact Wilcoxon rank sum test. Nonparametric bootstrap paired t ‐test also provided better performance than other alternatives. Nonparametric bootstrap test provided benefit over exact Kruskal–Wallis test. We suggest using nonparametric bootstrap test with pooled resampling method for comparing paired or unpaired means and for validating the one way analysis of variance test results for non‐normal data in small sample size studies. Copyright © 2017 John Wiley & Sons, Ltd.