Statistical power for nonequivalent pretest-posttest designs: The impact of change-score versus ANCOVA models

J. Michael Oakes, Henry A. Feldman

Research output: Contribution to journalArticlepeer-review

72 Scopus citations

Abstract

Nonequivalent controlled pretest-posttest designs are central to evaluation science, yet no practical and unified approach for estimating power in the two most widely used analytic approaches to these designs exists. This article fills the gap by presenting and comparing useful, unified power formulas for ANCOVA and change-score analyses, indicating the implications of each on sample-size requirements. The authors close with practical recommendations for evaluators. Mathematical details and a simple spreadsheet approach are included in appendices.

Original languageEnglish (US)
Pages (from-to)3-28
Number of pages26
JournalEvaluation Review
Volume25
Issue number1
DOIs
StatePublished - Feb 2001

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