Why sample size estimates?

Sample size estimates are critical to the planning and interpretation of clinical studies, whether they are descriptive or analytical. Too small a sample size will result in imprecise estimates in a descriptive study and failure to achieve 'statistical significance' in an analytic or comparative study. Here we discuss what both researchers and readers should understand about the reasons for sample size estimates, how they are done and how achieving or not achieving the desired sample size can affect the interpretation of the outcomes.