Probability sampling is one method of creating a sample group for research purposes. In this method, participants are selected at random. The random selection increases the odds that the sample group will more accurately represent the larger population.

For instance, if the larger population is comprised of 40 percent women and 60 percent men, the odds of a randomly selected person being a woman would be 40 percent. While a small sample of ten people selected at random might accidentally have eight women and two men, a large enough sample will correct this error. If you select 1,000 individuals for the sample group, you are more likely to end up with close to 400 women and 600 men. The numbers will rarely be that perfect, but the margin of error will be significantly lower the larger the sample group becomes.