Reading focus
Syllabus: How Do We Know What a Psychological Test Measures?
Translate the matrix’s trait–method combinations into concrete comparisons involving questionnaires, observers, and behavior.
Why you’re reading it. Test whether agreement reflects the intended attribute or the way it was measured.
A question to consider. Design a two-trait, two-method comparison for persistence and conscientiousness. Which pattern would make shared questionnaire method a plausible explanation?
Why this reading
Agreement between measures can reflect a shared attribute, a shared method, or both. The multitrait-multimethod matrix makes competing interpretations visible by combining several traits with several ways of measuring them.
Before you read
Convergent evidence concerns agreement across attempts to measure the same attribute. Discriminant evidence concerns distinctions between attributes. Method variance is variation associated with how measurements are obtained, such as a common rater or response format.
Read for
- Use the synthetic matrix to distinguish same-trait/different-method from different-trait/same-method correlations.
- Follow why evidence against unwanted convergence matters alongside expected agreement.
- Examine how the examples complicate the ideal pattern and the assumption that methods are independent.
Consider afterwards
- Self-reports of curiosity and sociability correlate more strongly than self- and observer-reports of curiosity. What explanations should a validation study distinguish?
Editorial context
This foundational framework identifies an evidential problem, not a rule that every large correlation validates a construct. Its interpretations depend on reliability, trait relationships, and method independence. A matrix helps organize competing explanations; it does not by itself identify a unique causal account.