Simple random sampling:-
We choose a sample of items in such a way that every sample of a given size has an equal chance of being selected.
We use a simple system to choose the sample, such as selecting every 10th or every 50th member of the population.
We use a sample that is convenient to select, such as people who happen to be in the same classroom.
We use this method when we are concerned about differences among subgroups, or strata, within a population. We first identify the subgroups and then draw a simple random sample within each subgroup. The total sample consists of all the samples from the individual subgroups.