Teacher’s Corner: A Note on Interpretation of the Paired-Samples t Test

Donald W. Zimmerman

Journal of Educational and Behavioral Statistics, 1997, vol. 22, issue 3, 349-360

Abstract: Explanations of advantages and disadvantages of paired-samples experimental designs in textbooks in education and psychology frequently overlook the change in the Type I error probability which occurs when an independent-samples t test is performed on correlated observations. This alteration of the significance level can be extreme even if the correlation is small. By comparison, the loss of power of the paired-samples t test on difference scores due to reduction of degrees of freedom, which typically is emphasized, is relatively slight. Although paired-samples designs are appropriate and widely used when there is a natural correspondence or pairing of scores, researchers have not often considered the implications of undetected correlation between supposedly independent samples in the absence of explicit pairing.

Keywords: correlated samples; difference scores; independent samples; matched pairs; nonindependence; paired samples; power; t test; Type I error; Type II error (search for similar items in EconPapers)
Date: 1997
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Persistent link: https://EconPapers.repec.org/RePEc:sae:jedbes:v:22:y:1997:i:3:p:349-360

DOI: 10.3102/10769986022003349

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