Step 4 8. W c samples Population is a large set or collection of items that have something in common. A sample is a subset of the population, selected in such a way that it is representative of the larger population. I methods of sampling The best way to ensure that a sample will lead to reliable inferences is to use probability samples in which the probability of being included in the sample is known for each subject in the population. First set sampling frame.
Every subject has an equal probability of being selected for the study.