Despite highly systematic methods for identifying priority problems and assessing intervention effects, the recent study by Tourgeman-Bashkin and colleagues would not be considered rigorous by conventional standards of validity, nor would its sample size of three units impress policymakers eager to promote large-scale change through improvement programs. Yet, study findings suggest that no sing...

This paper will explore if and how psychological strain plays a mediator role between the learning climate and job performance in a group of health workers. Although the relationship between learning climate and job performance has already been explored in the international literature, the role of psychological strain, which may hamper or deepen this relationship, has yet to be investigated. Th...

We have developed a new test against spurious long memory based on the invariance of long memory parameter to aggregation. By using the local Whittle estimator, the statistic takes the supremum among combinations of paired aggregated series. Simulations show that the test performs good in finite sample sizes, and is able to distinguish long memory from spurious processes with excellent power. M...

Sample size justification is required for all clinical studies. However, to many biomedical and clinical researchers, power and sample size analysis seems like a magic trick of statisticians. In this note, we discuss power and sample size calculations and show that biomedical and clinical investigators play a significant role in making such analyses possible and meaningful. Thus, power analysis...

We consider the problem of sample size determination for count data. Such data arise naturally in the context of multicenter (or cluster) randomized clinical trials, where patients are nested within research centers. We consider cluster-specific and population-averaged estimators (maximum likelihood based on generalized mixed-effect regression and generalized estimating equations, respectively)...

Sample size must be determined while planning a study to ensure that valid conclusions can be drawn when the study is over. different formulae for calculating the required size of the sample are used for different study designs and situations. A computer program is described here to ease the complexity of calculation of sample size for studies designed to use students 't' test.

Estimation of any probability distribution parameters is vital because imprecise and biased estimates can be misleading. In this study, we investigate a flexible power function distribution and introduced new two methods such as, probability weighted moments, and generalized probability weighted methods for its parameters. We compare their results with L-moments, trimmed L-moments by a simulati...

The authors describe 2 efficiency (planned missing data) designs for measurement: the 3-form design and the 2-method measurement design. The 3-form design, a kind of matrix sampling, allows researchers to leverage limited resources to collect data for 33% more survey questions than can be answered by any 1 respondent. Power tables for estimating correlation effects illustrate the benefit of thi...

1 USP 656 Multilevel Regression Winter 2013 Sample Size Issues and Power There are two sample size issues to be concerned about. One issue has to do with the minimum number of cases needed for using multilevel regression to avoid biases. The second issue concerns sufficient statistical power needed for obtaining significance. Generally, having more groups is more important than having more case...

Many researchers favor repeated measures designs because they allow the detection of within-person change over time and typically have higher statistical power than cross-sectional designs. However, the plethora of inputs needed for repeated measures designs can make sample size selection, a critical step in designing a successful study, difficult. Using a dental pain study as a driving example...