Statistics · Statistical sampling
Chapter 1 · 4
The idea
Non-random sampling — quota and opportunity
The two sampling methods that don't use chance: quota sampling (fill preset quotas for each group, choosing respondents non-randomly) and opportunity (or convenience) sampling (use whoever is available). How they work, when they're used, and why quota is not the same as stratified sampling.
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Statistics · Statistical sampling
Non-random sampling — quota and opportunity
The two sampling methods that don't use chance: quota sampling (fill preset quotas for each group, choosing respondents non-randomly) and opportunity (or convenience) sampling (use whoever is available). How they work, when they're used, and why quota is not the same as stratified sampling.
Why it works
When chance isn't available
Sometimes you have no sampling frame, or no time to build one, so a random method isn't available. Non-random sampling lets a person — not chance — pick the sample. It's quick and cheap, but because human choice is involved it risks bias: not every unit has a known chance of selection.Quota sampling
The researcher decides in advance how many to collect from each group — the quotas — chosen to reflect the population (e.g. "interview men and women"). They then approach people and slot them into the quotas until each is full, choosing who to ask themselves. No sampling frame is needed, which is why market researchers use it on the street.Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
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