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 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 ...

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 ...

I don't understand why they are using this method of calculating their sample size. I'm told if I use this I should start off with 5, 95 and 50 in the first, second and fourth boxes at the top.