Approaches to sampling commonly used in qualitative research design are given in Set-I and their characteristics in Set-II. 

Arjun singh

1. Extreme case sampling is a type of purposive sampling that is used to focus on cases that are are special or unusual, typically in the sense that the cases highlight notable outcomes, failure or success. 2. Purposive Sampling is a form of of non probability sampling in which researchers rely on their own judgement when choosing member of the population to participate in their study. 3. Snowball Sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find. If you satisfied with the answer kindly mark as best answer.

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1. Extreme Case Sampling focuses on participants with unique or special characteristics. An extreme case (or deviant case) can be thought of as an outlier an observation that takes on an extremely high or extremely low value. The general idea is that if you study extremes of the population, it could garner some valuable insights that can be generalized to the population as a whole.
2. A purposive sample is a non-probability sample that is selected based on characteristics of a population and the objective of the study. Purposive sampling is also known as judgmental, selective, or subjective sampling.
3. Snowball sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find. It’s called snowball sampling because (in theory) once you have the ball rolling, it picks up more “snow” along the way and becomes larger and larger.