Probability sampling methods are a type of sampling technique that uses random selection. The most important requirement of probability sampling methods is that every unit of the population has the same opportunity to be selected. That is to say, if there is a population of 100 people, each person would have a 1 in 100 chance of being selected. The probability sampling method provides researchers the best mechanism to create a representative sample of a population. The two most common types of probability sampling methods are simple random sampling and stratified random sampling. Simple random sampling is a method which assigns numbers to individuals and then randomly selects numbers through an automated process. Finally, the numbers that were chosen are the members that will be included in the sample. On the other hand, stratified random sampling requires to divide the population into mutually exclusive subgroups and then use simple random sampling to choose from each subgroup the members that will be included in the sample.