Sample size formula with a continuous outcome for unequal group sizes and unequal variances

Stat Med. 1999 Jan 15;18(1):87-91. doi: 10.1002/(sici)1097-0258(19990115)18:1<87::aid-sim958>;2-k.


Guenther derived a simple formula for the accurate computation of equal sample sizes when the two-sample t-test with pooled variance estimate is used. In the present paper, the Guenther formula is generalized to the case of unequal sample sizes. In addition, the case of unequal variances is considered.

MeSH terms

  • Analysis of Variance
  • Humans
  • Patients*
  • Sample Size*