title: Estimating standardized linear contrasts of means with desired precision.
abstract: L. Wilkinson and the Task Force on Statistical Inference (1999) recommended reporting confidence intervals for measures of effect sizes. If the sample size is too small, the confidence interval may be too wide to provide meaningful information. Recently, K. Kelley and J. R. Rausch (2006) used an iterative approach to computer-generate tables of sample size requirements for a standardized difference between 2 means in between-subjects designs. Sample size formulas are derived here for general standardized linear contrasts of k > or = 2 means for both between-subjects designs and within-subjects designs. Special sample size formulas also are derived for the standardizer proposed by G. V. Glass (1976).
authors.affiliation: Department of Statistics, Iowa State University, Ames 50011, USA. dgbonett@iastate.edu
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Bonett
mesh_terms: D016001:Confidence Intervals; D006801:Humans; D016014:Linear Models; D008960:Models, Psychological; D011589:Psychology, Experimental / Q000592:standards / Q000706:statistics & numerical data*; D012107:Research Design / Q000592:standards / Q000706:statistics & numerical data; D018401:Sample Size