We present a simple sample-size formula for weighted log-rank statistics applied to clustered survival data with variable cluster sizes and arbitrary treatment assignments within clusters. This ...

The formula for the sample size for a difference from a mean is: where tα and tβ are the one sided t distribution values for the given α and β risk levels selected and S2 is the variance of the total ...

Course TopicsPower analyses and sample size calculations are important parts of many research projects. Often, before data are even collected, it is necessary to calculate and justify the required ...

The standard formulas used to calculate sample size for an individually matched case-control study assume a constant probability of exposure throughout the pool of possible controls. We propose new ...

This webinar provides some practical and useful answers to this question. Methods for determining appropriate sample sizes in raw materials acceptance, finished product release, process and product ...

For heterogeneous populations, a sample size of 2K is unlike the spoonful of soup. Accordingly, results of surveys conducted with such a sample may not be valid for the population.