**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.

**Systematic sampling:-**

We use a simple system to choose the sample, such as selecting every 10^{th} or every 50^{th} member of the population.

**Convenience sampling:-**

We use a sample that is convenient to select, such as people who happen to be in the same classroom.

**Stratified sampling:-**

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.