Sample size planning with the cost constraint for testing superiority and equivalence of two independent groups

Jiin Huarng Guo, Hubert J. Chen, Wei-Ming Luh

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

The allocation of sufficient participants into different experimental groups for various research purposes under given constraints is an important practical problem faced by researchers. We address the problem of sample size determination between two independent groups for unequal and/or unknown variances when both the power and the differential cost are taken into consideration. We apply the well-known Welch approximate test to derive various sample size allocation ratios by minimizing the total cost or, equivalently, maximizing the statistical power. Two types of hypotheses including superiority/non-inferiority and equivalence of two means are each considered in the process of sample size planning. A simulation study is carried out and the proposed method is validated in terms of Type I error rate and statistical power. As a result, the simulation study reveals that the proposed sample size formulas are very satisfactory under various variances and sample size allocation ratios. Finally, a flowchart, tables, and figures of several sample size allocations are presented for practical reference.

Original languageEnglish
Pages (from-to)439-461
Number of pages23
JournalBritish Journal of Mathematical and Statistical Psychology
Volume64
Issue number3
DOIs
Publication statusPublished - 2011 Nov 1

All Science Journal Classification (ASJC) codes

  • Statistics and Probability
  • Arts and Humanities (miscellaneous)
  • Psychology(all)

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