Sample size, power concepts and sample size calculation

Sample size calculation: Basic principles

Addressing a sample size is a practical issue that has to be solved during planning and designing stage of the study. The aim of any clinical research is to detect the actual difference between two groups (power) and to provide an estimate of the difference with a reasonable accuracy (precision). Hence, researchers should do a priori estimate of sample size well ahead, before conducting the stu...

Principles of sample size calculation

In most areas in life, it is difficult to work with populations and hence researchers work with samples. The calculation of the sample size needed depends on the data type and distribution. Elements include consideration of the alpha error, beta error, clinically meaningful difference, and the variability or standard deviation. The final number arrived at should be increased to include a safety...

Sample Size and Statistical Power Calculation in Genetic Association Studies

A sample size with sufficient statistical power is critical to the success of genetic association studies to detect causal genes of human complex diseases. Genome-wide association studies require much larger sample sizes to achieve an adequate statistical power. We estimated the statistical power with increasing numbers of markers analyzed and compared the sample sizes that were required in cas...

Sample Size Calculation and Power Analysis of Time-Averaged Difference

Sample Size Issues and Power

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...