Tool 01
Sample size calculator
For: Anyone writing a synopsis or answering a committee's query about numbers
The four designs most postgraduate theses use — estimating a prevalence, comparing two means, comparing two proportions and diagnostic accuracy — plus correlation. It shows the formula, the values substituted into it, and the arithmetic, so you can defend the number rather than only quote it.
What it gives you
- The required n, per group and in total, rounded up
- Attrition applied, so the figure you write is the figure you recruit to
- A methods sentence you can paste into your synopsis, with your own citation to fill in
- The questions an examiner tends to ask about it