1981/06/01 by Larry V. Hedges · 9 citations
Mathematics · Decision Sciences · #Advanced Statistical Methods and Models #Statistical Methods in Clinical Trials #Optimal Experimental Design Methods #Estimator #Minimum-variance unbiased estimator #Bias of an estimator #Statistics #Mathematics #Sample size determination #Stein's unbiased risk estimate #Trimmed estimator #Efficient estimator #Consistent estimator #Invariant estimator #Context (archaeology) #Variance (accounting) #Efficiency #Standard deviation #Mean squared error #Applied mathematics
paper · doi:10.3102/10769986006002107
openalex publication_date 1981/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
Glass's estimator of effect size, the sample mean difference divided by the sample standard deviation, is studied in the context of an explicit statistical model. The exact distribution of Glass's estimator is obtained and the estimator is shown to have a small sample bias. The minimum variance unbiased estimator is obtained and shown to have uniformly smaller variance than Glass's (biased) estimator. Measurement error is shown to attenuate estimates of effect size and a correction is given. The effects of measurement invalidity are discussed. Expressions for weights that yield the most precise weighted estimate of effect size are also derived.