This article explains how to choose the right number of people for a study and how to pick them in a fair way. To make sure the results can be applied to a larger group, the sample needs to be big enough and selected using specific methods. Factors like the size of the group being studied, how sure you want to be about the results, and how much accuracy you need all play a role in determining the sample size. Methods like random sampling, systematic sampling, and others are better for health research because they give more reliable results that can be applied to a larger group.