Continuous Outcomes

This chapter considers sample‐size calculations for comparisons between means of groups where the outcome of concern is continuous. It describes the situations when the data can be assumed to have a Normal distribution form, and when they do not. The chapter also describes the problem of comparing an estimated mean from one group with an assumed known mean in the other. A continuous variable is one that, in principle, can take any value within a range of values. Continuous variables may be distributed Normally, meaning they have a characteristic bell‐shaped curve which is completely determined by the mean and standard deviation. In such cases, groups are compared using the respective means and the corresponding t‐test. If the data collected are from a continuous outcome variable plausibly sampled from a Normal distribution, then the appropriate summary statistic is the mean.