Your Easy Guide to Clinical Studies

When planning a study, it is important to justify the defined sample size of the study (i.e. number of participants included in the study).

 

The sample size will have a direct effect on the precision and accuracy of study results, including the ability to detect a real effect.

 

As a SP-INV, based on the aim of your study explain how the sample size and its subsequent collected data are expected to provide valuable scientific information.

 

Aspects to consider include:

• The outcome/endpoint of your study (e.g. cholesterol concentration)
• The method you use for the sample size estimation
• The statistical framework, which can either be:
  • Hypothesis testing (e.g. you want to test the difference in cholesterol concentration between two patient groups). Define the null and alternative hypothesis
  • Precision-based (e.g. you want to estimate the mean in cholesterol concentration of a certain group of patients). Define the type I error and power
• The assumption/previous knowledge which were used as a basis for the sample size calculation (e.g. we expect a mean value of 5.2 mmol/L and a standard deviation of 1.5)

References

ICH Topic E9 – see in particular

• 3.5 Sample Size