# Introduction

When designing a new study, a very useful exercise to carry out is that of determining an appropriate sample size. This is an important step in helping to ensure that the study achieves the outcomes it set out to achieve. As you may be able to imagine, if the sample size is not big enough, then the results of the study may not be strong enough to draw any significant or meaningful conclusions. On the other hand, increasing the sample size can come at a cost in many situations. This is why choosing an appropriate sample size is so important - so that a balance between these competing factors can be found. Sample size calculations are very much related to the concept of statistical power, which we will learn about in the next section. We will then look at some example sample size calculations for $$t$$-tests and the two-sample test of proportions.