What it shows
Quota sampling begins as stratified sampling does, by dividing the population into groups that do not overlap. Here group A has 48 units and group B has 72, a ratio of 2 : 3, and the quotas of 4 and 6 keep that ratio.
The interviewer then fills each quota with the nearest units rather than drawing at random within each group. That non-random step makes quota sampling a nonprobability method.
How to read it
The two groups are labeled above the grid.
Filled circles are the units chosen to fill each quota.
They sit close together near the interviewer rather than spread across each group.
The numbers behind it
- Population of 120: group A, 48 units; group B, 72 units (2 : 3).
- Quotas: 4 from group A and 6 from group B.
Ways to use it in teaching
Compare it with stratified random sampling, which uses the same groups but draws at random within them.
Ask what a quota guarantees (the mix of groups) and what it does not (an equal chance for everyone in each group).
Students can set quotas for a population of their own from real proportions.
For when each method suits a study, and how to justify the choice in a methodology chapter, see our guide to sampling methods.
Sources
The ratio follows the 200 : 300 example in Wikipedia's Quota sampling article.
