Here's a simple way to show how a researcher can remove bias when conducting simple random sampling. Let's say there are 100 bingo balls in a bowl, from which the researcher must choose 10.

Samples are randomly chosen from each proportional to the group’s size vs. the population. Stratified random sampling offers some advantages and disadvantages compared to simple random sampling.

Over the years, the margin of sampling ... poll’s overall accuracy. That simple idea requires some critical assumptions, however: It presumes that the sample was chosen completely at random ...