Lesson 3 of 8 · 12 min

Convenience and judgmental sampling, and choosing a method

Non-probability samples are chosen by convenience or expert judgment: quick and cheap, but at real risk of not representing the population.

In short

Non-probability methods rely on the researcher's selection, not on a fixed random process, so not every member has an equal chance of being chosen.
Convenience sampling: use what is easiest to access. Fast and low cost, ideal for a pilot study, but the sample may not represent the population, so accuracy can be limited.
Judgmental sampling: an expert handpicks members. Useful under time pressure or when expertise is critical (e.g. auditing), but exposed to the researcher's bias.
Probability methods let chance alone drive sampling error; non-probability methods add the risk of a systematically unrepresentative sample.
Match the method to the goal: inference about a population → probability sampling; index replication → stratified; vast population on a budget → cluster; quick first look → convenience.

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