In the last paper in this miniseries, we identified the approach taken to generating a study sample for experimental studies; more specifically we examined randomised controlled trials (RCTs). We saw how in RCTs it is important to take account of generalisability, homogeneity and the management of bias. We identified the sampling approach as being probability sampling, ensuring all people within the study population have an equal chance of being selected for the study. We also demonstrated how randomisation within the