Convergent Validity
Convergent validity is the extent to which a measure correlates with other measures of the same or theoretically related constructs. With discriminant validity it forms the conceptual core of construct validation introduced by Campbell and Fiske through the multitrait-multimethod (MTMM) matrix.
The MTMM matrix
Campbell and Fiske proposed that construct validity requires evidence on two fronts simultaneously: measures of the same trait taken by different methods should correlate strongly (convergence), and measures of different traits should correlate weakly even when they share a method (discrimination). The MTMM matrix arranges trait–method correlations so that monotrait–heteromethod values can be inspected against heterotrait–monomethod and heterotrait–heteromethod values. Convergence is supported when monotrait–heteromethod correlations are substantial; failure to converge across methods raises doubt about whether the trait is being measured at all.
Application in language testing
In language assessment, convergent evidence might compare a new oral proficiency interview with an existing speaking test, a self-rating instrument, or teacher ratings of the same examinees. Substantial correlations across these methodologically distinct measures support the inference that the new instrument taps the speaking-proficiency construct. The same logic underlies confirmatory factor analyses in which indicators of one factor are expected to load strongly on it; the average variance extracted (AVE) and composite reliability are commonly reported as convergent indices in modern construct-validation work.
Convergent evidence is necessary but not sufficient: correlations could reflect shared method variance or a more general factor rather than the targeted trait, which is why discriminant evidence is examined alongside it.
References
- Campbell, D. T., & Fiske, D. W. (1959). Convergent and discriminant validation by the multitrait-multimethod matrix. Psychological Bulletin, 56(2), 81–105.
- Bachman, L. F. (1990). Fundamental Considerations in Language Testing. Oxford University Press.
- Messick, S. (1989). Validity. In R. L. Linn (Ed.), Educational Measurement (3rd ed., pp. 13–103). American Council on Education / Macmillan.