Sample size and power calculations using the noncentral t–distribution
Abstract. The standard formulas for sample size and power calculation, as implemented
in the command sampsi, make use of a normal approximation to the
t-distribution. When the sample sizes are small, this approximation is poor,
resulting in overestimating power (or underestimating sample size). One
particular situation in which this is likely to be important is the field of
cluster randomized trials. Although the total number of individuals in a
cluster randomized trial may be large, the number of clusters will often be
small. We present a simulation study from the design of a cluster randomized
crossover trial that motivated this work and a command to perform more
accurate sample size and power calculations based on the noncentral
t-distribution.
View all articles by these authors:
David A. Harrison, Anthony R. Brady
View all articles with these keywords:
sampncti, sample size, power, noncentral t-distribution
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