Incremental validity is a type of
statistical validity that assesses whether a new
psychometric
Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and rela ...
assessment has more predictive ability than existing methods of assessment.
It seeks to determine whether the new assessment adds information that cannot be obtained with simpler, already existing methods.
[Lillenfield et al. 2005 "What's wrong with this picture?" ''www.psychologicalscience.org'' http://www.psychologicalscience.org/newsresearch/publications/journals/sa1_2.pdf ]
New psychometric instruments are often assessed on whether it can increase knowledge of an outcome variable beyond what is already known based on existing instruments.
[ ] If the instrument is less successful than an existing tool, then it is incrementally invalid.
Incremental validity is usually assessed using
multiple regression methods, involving a regression model with other variables fitted to the data and another model with the focal variable added. Using an
F-test
An F-test is a statistical test that compares variances. It is used to determine if the variances of two samples, or if the ratios of variances among multiple samples, are significantly different. The test calculates a Test statistic, statistic, ...
to determine
significance, a significant difference in the
R-square statistic reflects the percent of variance explained by the added variable, indicating whether that variable offers significant additional predictive power for the dependent variable over other variables. Using the change in R-square is more appropriate than mere raw correlations, because the raw correlations do not reflect the overlap of the newly introduced measure and the existing measures.
For example, the
College Board
The College Board, styled as CollegeBoard, is an American not-for-profit organization that was formed in December 1899 as the College Entrance Examination Board (CEEB) to expand access to higher education. While the College Board is not an asso ...
has used multiple regression models to assess the incremental validity of a revised SAT test.
See also
*
Predictive validity
*
Criterion validity In psychometrics, criterion validity, or criterion-related validity, is the extent to which an operationalization of a construct, such as a test, relates to, or predicts, a theoretically related behaviour or outcome — the criterion. Criterion vali ...
References
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Validity (statistics)