The general formulation of a linear combination of population means permits a wide range of research questions to be tested within the context of ANOVA. However, it has been stressed in many research areas that the homogeneous variances assumption is frequently violated. To accommodate the heterogeneity of variance structure, the Welch–Satterthwaite procedure is commonly used as an alternative ...

Comparing treatment effects by hypothesis testing is a common practice in plant pathology. Nearest percent estimates (NPEs) of disease severity were compared with Horsfall-Barratt (H-B) scale data to explore whether there was an effect of assessment method on hypothesis testing. A simulation model based on field-collected data using leaves with disease severity of 0 to 60% was used; the relatio...

This paper addresses the question of which large–sample binomial confidence interval method to teach in elementary courses. Recently, Goodall (1995), Simon (1996), and the references therein, have discussed the merits of several large–sample systems of binomial intervals. Three of the systems considered these articles are the z-interval, a “t-based interval,” and a continuitycorrected interval,...

BACKGROUND Elderly patients represent the greatest consumers of healthcare per capita but have historically been underrepresented in clinical trials. It is unknown how many trials are designed to focus exclusively on elderly patients. OBJECTIVE To define the prevalence of interventional trials that study exclusively elderly persons and describe the characteristics of these trials, including t...

PURPOSE The aim is of this study was to show the poor statistical power of postmortem studies. Further, this study aimed to find an estimate of the effect size for postmortem studies in order to show the importance of this parameter. This can be an aid in performing power analysis to determine a minimal sample size. METHODS GPower was used to perform calculations on sample size, effect size, ...

BACKGROUND The smallest difference to be detected in superiority trials or the largest difference to be ruled out in noninferiority trials is a key determinant of sample size, but little guidance exists to help researchers in their choice. The objectives were to examine the distribution of differences that researchers aim to detect in clinical trials and to verify that those differences are sma...

In the analysis of microarray data, and in some other contemporary statistical problems, it is not uncommon to apply hypothesis tests in a highly simultaneous way. The number, ν say, of tests used can be much larger than the sample sizes, n, to which the tests are applied, yet we wish to calibrate the tests so that the overall level of the simultaneous test is accurate. Often the sampling distr...

As is convincingly demonstrated in the target article (Simons et al., 2016, this issue), despite the numerous forms of brain training that have been tested and touted in the past 15 years, there’s little to no evidence that currently existing programs produce lasting, meaningful change in the performance of cognitive tasks that differ from the trained tasks. As detailed by Simons et al., numero...

MOTIVATION Microarray data typically have small numbers of observations per gene, which can result in low power for statistical tests. Test statistics that borrow information from data across all of the genes can improve power, but these statistics have non-standard distributions, and their significance must be assessed using permutation analysis. When sample sizes are small, the number of dist...