Content validity asks whether an instrument covers all relevant parts of the concept being measured. Criterion-related validity asks whether its results agree with or predict an appropriate external benchmark, called a criterion.
This distinction is part of AHL 4.12: Data collection, reliability and validity tests and is therefore HL-only content in IB Mathematics: Applications and Interpretation.
How Each Type of Validity Works
Suppose researchers design a questionnaire to measure students' academic stress.
For content validity, they check whether the questions represent the full construct. A suitable questionnaire could include workload, deadlines, examinations, time pressure and expectations. If it asks only about examinations, it lacks content validity because important dimensions are omitted.
For criterion-related validity, researchers compare questionnaire scores with an accepted external measure, such as an established stress assessment. A strong relationship provides evidence of criterion-related validity. The criterion can be measured at the same time or be a future outcome that the questionnaire is intended to predict.
| Feature | Content validity | Criterion-related validity |
|---|---|---|
| Main question | Does the instrument cover the whole construct? | Do the results agree with or predict an external criterion? |
| Evidence used | Expert judgement and coverage of relevant categories | Comparison with an accepted benchmark or outcome |
| Typical weakness | Important aspects are omitted | The criterion is unsuitable or the relationship is weak |
| Example | A stress survey includes all major sources | Survey scores correspond with an established assessment |
A common misconception is that strong criterion-related validity automatically proves content validity. It does not: an instrument may correlate with a benchmark while still omitting part of the construct. Similarly, reliability means consistency, not validity.
Exam Technique
In an IB response, identify the type and justify it using the scenario. Write “content validity because all relevant dimensions are represented” or “criterion-related validity because results are compared with an external benchmark.” A label alone is insufficient.
