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 ...

This study discusses the sample size requirement for the Welch test in the one-way fixed-effect analysis of variance with unknown and possibly unequal variances. The authors propose a formula of ...

Given the unacceptable quality of the sample size calculation of COVID-19 trials, I strongly suggest that all research teams include a statistician or invite a statistician to evaluate the ...