An important step when designing an empirical study is to justify the sample size that will be collected. The key aim of a justification for such studies explain how collected data expected provide valuable information given inferential goals researcher. In this overview article six approaches are discussed in quantitative study: 1) collecting from (almost) entire population, 2) choosing based ...

The number of individuals to include in a research study, the sample size of the study, is an important consideration in the design of many clinical studies. This article reviews the basic factors that determine an appropriate sample size and provides methods for its calculation in some simple, yet common, cases. Sample size is closely tied to statistical power, which is the ability of a study ...

BACKGROUND Effect size reporting and interpreting practices have been extensively recommended in academic journals when analyzing primary outcomes of all empirical studies. Accordingly, the sample squared multiple correlation coefficient is the commonly reported strength of association index in practical applications of multiple linear regression. METHOD This paper examines the sample size pr...

Adaptive designs have been proposed for clinical trials in which the nuisance parameters or alternative of interest are unknown or likely to be misspecified before the trial. Although most previous works on adaptive designs and mid-course sample size re-estimation have focused on two-stage or group-sequential designs in the normal case, we consider here a new approach that involves at most thre...

It is widely assumed that 5 participants suffice for usability testing. In this study, 60 users were tested and random sets of 5 or more were sampled from the whole, to demonstrate the risks of using only 5 participants and the benefits of using more. Some of the randomly selected sets of 5 participants found 99% of the problems; other sets found only 55%. With 10 users, the lowest percentage o...

A total of 1,734 adults performed two running memory tasks and a battery of cognitive tests representing four cognitive abilities. Simultaneous analyses were used to identify unique relations of each cognitive ability, including fluid intelligence, on the running memory measures. The large sample size allowed powerful analyses of the relations at the level of individual trials, separate list le...

BACKGROUND Different preference-based measures (PBMs) used to estimate quality-adjusted life years (QALYs) provide different utility values for the same patient. Differences are expected since values have been obtained using different samples, valuation techniques, and descriptive systems. Previous studies have estimated the relationship between pairs of PBMs using patient self-reported data. H...