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 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 ...

The relationship between sample size and the difference you consider worth looking for follows the inverse square law: if you halve the size of the difference, you quadruple the number of patients ...

Some notes on the behaviour of sample size calculations and power for unequal group sizes This information was omitted from the video and so is included here as text. In many scenarios the ratio of ...

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 ...

T-tests are best performed when the data consists of a small sample size, i.e., less than 30. T-tests assume the standard deviation is unknown, while Z-tests assume it is known.