Randomization tests and the unequal-N/unequal-variance problem

D. J.K. Mewhort, Matthew Kelly, Brendan T. Johns

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


When both the variance and the N are unequal in a two-group design, the probability of a Type I error shifts from the nominal 5% error rate. The probability is too liberal when the small cell has the larger variance and too conservative when the large cell has the larger variance. We present an algorithm to circumvent the problem when the smaller group has the larger variance and show, by simulation, that the algorithm brings the error rate back to the nominal value without sacrificing the ability to detect true effects.

Original languageEnglish (US)
Pages (from-to)664-667
Number of pages4
JournalBehavior research methods
Issue number3
StatePublished - Aug 2009

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • Developmental and Educational Psychology
  • Arts and Humanities (miscellaneous)
  • Psychology (miscellaneous)
  • General Psychology


Dive into the research topics of 'Randomization tests and the unequal-N/unequal-variance problem'. Together they form a unique fingerprint.

Cite this