15.4  Non-probability sampling methods

Samples selected using non-probability sampling methods are not representative samples and their findings cannot be generalised to the whole study population from which the sample was taken. This is because the individuals in the sample are chosen by ‘hand picking’ and therefore the people in the study population do not each have an equal chance of being selected. You may use non-probability sampling methods for defined purposes, e.g. if you wanted to investigate knowledge, attitudes and practice regarding female genital mutilation (FGM) in your community. A non-probability type of sampling would be appropriate in this case because you would want to interview people who can shed light on this sensitive subject. The types of non-probability sampling methods that you might use in such a study include purposeful sampling, quota sampling and snowball sampling.