# What is the difference between probability and non-probability sampling?

Quantitative Methodology

If you are conducting an original study for your dissertation research, you will need to choose a method of sampling to obtain your participants. Choosing an appropriate sampling method is important for both quantitative and qualitative studies. There are two general types of sampling methods: probability sampling and non-probability sampling. In this blog, we will explain these two types of sampling and when it is appropriate to use them.

The first type of sampling is probability sampling, which will always involve some sort of “random” or “probabilistic” process to select participants. The various forms of random sampling (including simple random sampling and stratified random sampling) are probability sampling techniques. In the most basic form of probability sampling (i.e., a simple random sample), every member of the population has an equal chance of being selected into the study. The participants selected for the study would be determined through some kind of “random” process, such as assigning a number to every member of the population and picking the numbers out of a hat, or using a table of randomly generated numbers. More complex forms of probability sampling (such as stratified random sampling) involve randomly selecting individuals from subgroups of the population to ensure those groups are appropriately represented in the study sample. 