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 ...

Sample size determination is an important issue in planning research. In the context of one-way fixed-effect analysis of variance, the conventional sample size formula cannot be applied for the ...

Cheung and colleagues warned that underpowered studies that committed a type II error will discourage clinicians from using effective treatment.1 I agreed with this ...