Probability and non-probability sampling are techniques utilized to select part of a target population to conduct a survey. Probability sampling refers to a sampling method that involves the probability theory whereby the likelihood of any unit’s knowledge of being selected is employed (Langer 2018). Therefore, every target population member has an equal selection chance. Some probability sampling methods are cluster sampling, stratified sampling, systematic sampling, and simple random sampling. The non-probability sampling technique, to the contrary, doesn’t give all target population members equal chances of selection for participation in a study. This makes the selection chances of each target population member pre-determined and known. It, therefore, allows the researcher to use subjective judgment in the sample selection and not a random selection.
Probability sampling has been used in the first instance, where a manager goes to the discharge area to interview the leaving patients. All patients leaving the hospital have equal chances of being interviewed because they leave via the same area. The second instance involves nurses on the floor distributing questionnaires to all patients to complete before returning them to the discharge counter as they leave. In this particular instance, it should be noted that nurses’ judgment is not utilized to determine participants in the survey.
Since each member has a chance of participating, then it signifies that probability sampling has been employed. In the third instance, the CEO selects some patients randomly from a particular group (those about to be discharged). This shows that the CEO employs judgment to collect the samples, amounting to non-probability sampling (Etikan&Bala, 2017). The last instance sees the patients grouped by departments by the CEO and a patient randomly selected from each department. Therefore, the chances of a patient being selected from every department are known, amounting to non-probability sampling.
References
Etikan, I., &Bala, K. (2017). Sampling and sampling methods. Biometrics & Biostatistics International Journal, 5(6), 00149.
Langer, G. (2018). Probability versus non-probability methods. In The Palgrave Handbook of Survey Research (pp. 351-362). Palgrave Macmillan, Cham.