When designing a study to compare the outcomes of an intervention, an essential step is the calculation of sample sizes that will allow a reasonable chance (power) of detecting a predetermined difference (effect size) in the outcome variable, at a given level of significance. Sample size is critically dependent on the proposed effect size: half the effect size and the sample size is quadrupled....

Background. Averaged Norbeck Social Support Questionnaire (NSSQ) support scores remove the influence of network size variability but may unduly lower scores for participants with large networks. Objectives. To evaluate the use of averaged NSSQ scores. Method. Pearson correlations determined if averaged scores decreased as network size increased across three samples. Then, Pearson correlations b...

Throughout the mid to late 1970's considerable research was conducted on the properties of Rasch fit mean squares. This work culminated in a variety of transformations to convert the mean squares into approximate t-statistics. This work was primarily motivated by the influence sample size has on the magnitude of the mean squares and the desire to have a single critical value that can generally ...

The present review introduces the notion of statistical power and the hazard of under-powered studies. The problem of how to calculate an ideal sample size is also discussed within the context of factors that affect power, and specific methods for the calculation of sample size are presented for two common scenarios, along with extensions to the simplest case.

Methods of sample size planning are developed from the accuracy in parameter approach in the multiple regression context in order to obtain a sufficiently narrow confidence interval for the population squared multiple correlation coefficient when regressors are random. Approximate and exact methods are developed that provide necessary sample size so that the expected width of the confidence int...

People often estimate the average duration of several events (e.g., on average, how long does it take to drive from one's home to his or her office). While there is a great deal of research investigating estimates of duration for a single event, few studies have examined estimates when people must average across numerous stimuli or events. The current studies were designed to fill this gap by e...

The world of robot soccer is a subjective one due to the di cult nature of collecting data. In this paper we present a number of non-parametric statistical tests that can be used to analyze the performance of strategies without the need for a large sample size. We present results that show a \case-based" strategy performs signi cantly better (statistically) than a \potential eld" strategy in si...

BACKGROUND To assess examination related anxiety among first professional medical students and to determine the factors contributing to this kind of anxiety among them. METHODS A cross-sectional study using structured self-administered questionnaire was carried out over 10 days in Frontier Medical and Dental College, Abbottabad, in December 2012, using sample size of 200 students,. Survey que...

Recent controversies have questioned the quality of scientific practice in the field of psychology, but these concerns are often based on anecdotes and seemingly isolated cases. To gain a broader perspective, this article applies an objective test for excess success to a large set of articles published in the journal Psychological Science between 2009 and 2012. When empirical studies succeed at...

S tatistical analysis is an important tool in experimental research and is essential for the reliable interpretation of experimental results. It is essential that statistical design should be considered at the very beginning of a research project, not merely as an afterthought. For example if the sample size for an experiment only allows for an underpowered statistical analysis, then the interp...