Which of the following sampling methods is based on probability?

Concept

Probability sampling uses a known random mechanism so that each population unit has a known, non-zero chance of selection.

Non-probability sampling instead depends on accessibility, fixed quotas, or the researcher’s judgement rather than random selection.

Application

In stratified sampling, the population is first divided into relevant, non-overlapping strata. A random sample is then selected from each stratum, so the selection stage is probability-based.

Contrast

• Convenience sampling chooses units that are easiest to reach.

• Quota sampling fills preset category quotas without requiring random selection within each quota.

• Judgement sampling lets the researcher deliberately choose units considered informative.

• Stratified sampling combines population strata with random selection inside those strata.

Cross-check

Only stratified sampling specifies a random selection mechanism among the offered methods; therefore, the probability-based method is stratified sampling.