Journal of Statistical Theory and Practice

, Volume 1, Issue 2, pp 253–264 | Cite as

Sample Size Re-Estimation: Nonparametric Approach

  • Z. GovindarajuluEmail author


A question of importance that arises in clinical trials pertains to the number of additional observations, if any, that are required beyond those initially planned. This has been answered in the case of two-treatment double blind clinical experiment via a nonparametric approach in which the mean and the variance of the underlying populations are not functionally related. In this paper, a totally nonparametric approach is taken. We will be interested in testing the equality of two treatment effects against the alternative that one effect is stochastically larger than the other. Using Mann-Whitney-Wilcoxon test criterion, the robustness of the sample size in terms of the level of significance and power of a specified nonparametric alternative is established. This procedure is applied to the data pertaining to blood cholesterol levels in samples drawn from two different age groups.

AMS Subject Classification



Robustness Clinical trials Double-blind experiment Sample size re-estimation Arbitrary populations 


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Copyright information

© Grace Scientific Publishing 2007

Authors and Affiliations

  1. 1.Department of StatisticsUniversity of KentuckyUSA

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