Definition of Validity

Accuracy + Repeatability (Reliability) = True validity

Measurement Validity

Determines if the method used to measure a variable truly measures that variable.

Example of Measurement Validity

Using a mood scale to measure pain—appropriate only if it includes relevant subscales.

Types of Measurement Validity

Face Validity
Content Validity
Construct Validity
Criterion Validity

Face Validity

Tool includes questions on pain level, mobility, and lifestyle → seems valid.

Example Face Validity

Tool includes questions on pain level, mobility, and lifestyle → seems valid.

Content Validity

Assesses if all relevant aspects of the construct are covered.

No inclusion of irrelevant content.

Example Content Validity

Balance test should not include recumbent positions.

Construct Validity

Degree to which a tool measures the theoretical construct it claims to.

Subtypes of Construct Validity

Convergent Validity
Discriminant (Divergent) Validity

Convergent Validity

Test aligns with other accepted tools measuring the same construct.

Discriminant (Divergent) Validity

Tool distinguishes between related but distinct constructs.

Example Discriminant (Divergent) Validity

Differentiating between socioeconomic status and lifestyle in relation to pain.

Criterion Validity

Compares a test with a gold standard.

Common in diagnostic and outcome measure studies.

Subtypes of Criterion Validity:

Concurrent Validity: Test and gold standard used at the same time.

Predictive Validity: Test predicts future outcomes.

Example: Clinical exam vs. MRI for soft tissue damage.

Research Validity

Concerned with whether the study’s results are accurate and applicable.

Internal Validity

Confidence that observed effects are due to the intervention, not confounding factors.

Applies to experimental and quasi-experimental designs.

Often referred to as believability: Can I trust the results?

External Validity

Ability to generalize results to different settings, populations, or times.

Example: Study results from Japan—are they applicable in your clinic?

Diagnostic Validity

Evaluates diagnostic test accuracy.

Determines how well a test identifies a condition.