Determining Sample Sizes for Precise Contrast Analysis With Heterogeneous Variances

The analysis of variance (ANOVA) is one of the most frequently used statistical analyses in practical applications. Accordingly, the single and multiple comparison procedures are frequently applied to assess the differences among mean effects. However, the underlying assumption of homogeneous variances may not always be tenable. This study examines the sample size procedures for precise interval estimation of linear contrasts within the context of one-way heteroscedastic ANOVA models. The desired precision of both individual and simultaneous confidence intervals is evaluated with respect to the control of expected half width and to the tolerance probability of interval half width within a designated value. Supplementary computer programs are developed to aid the usefulness and implementation of the proposed techniques. The suggested sample size procedures improve upon the existing approaches and extend the methodology development in the statistical literature.