What it shows
Convenience sampling takes the units that are easiest to reach. In the diagram the researcher stands at one point and takes the 8 units closest by straight-line distance; a dashed line encloses exactly those 8.
The units are not numbered, because there is no sampling frame. This is one of the four nonprobability methods in the set.
How to read it
Filled circles are selected; open circles are the rest of the population.
The dashed line marks the area close at hand. Every unit inside it is in the sample.
Units outside the line had no chance of selection, which limits how far results from such a sample can be generalized.
The numbers behind it
- Population of 120 units in rows of 15.
- Sample: the 8 units nearest the researcher, by straight-line distance.
Ways to use it in teaching
Students can name convenience samples they have taken part in, such as a questionnaire handed round a lecture hall.
Discuss legitimate uses, such as piloting a questionnaire before the main study.
Set it beside the simple random sample and ask which units could never appear in this one.
For when each method suits a study, and how to justify the choice in a methodology chapter, see our guide to sampling methods.
