Incremental Validity
Definition
The improvement in predictive accuracy that a test adds over and above prior information; justifies the cost and burden of additional assessment.
- Field
- Psychometric test evaluation
- Measures
- Gain in predictive accuracy over existing information alone
- Use case
- Justifies adding a test to an assessment battery
Common questions
Why does a test with strong validity still need incremental validity evidence?+
A test can correlate well with an outcome on its own yet add nothing once file review, interview, and other measures are already in hand, so an examiner must show the test still improves prediction after accounting for what the evaluator already knows.
How is incremental validity relevant to a forensic evaluator choosing tools?+
Adding tests costs evaluee time and case delay, so an evaluator who cannot show a new instrument improves accuracy over the existing battery is exposed to cross-examination on why it was administered at all.
Related terms
- AUC Statistic
- Area under the receiver operating characteristic curve; the standard criterion-validity metric for forensic risk and malingering instruments, with 0.70 considered a minimum...
- Base Rate
- The prior probability of an event or proposition before specific evidence is considered. In forensic inference, the base rate is the probability...
- BSA 2023 § 39
- Section 39 of the Bharatiya Sakshya Adhiniyam 2023, the provision governing expert opinion evidence in Indian courts. Replaced Indian Evidence Act 1872...
- Consequential Validity
- The fairness and equity implications of test use; includes disparate impact on racial or cultural groups and the systematic bias this may...
- Criterion Validity
- The degree to which test scores predict or correlate with an external criterion; predictive criterion validity is most relevant to forensic instruments.
- Daubert Standard
- The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
- Ecological Validity
- The degree to which a measurement or test procedure produces results that generalise from the controlled laboratory context to the real-world condition...
- Positive Predictive Value (PPV)
- The probability that a person who tests positive on a risk instrument will actually reoffend. PPV depends on both the instrument's sensitivity...
- Reliability
- The extent to which a measurement procedure produces the same result when repeated under the same conditions or by a different researcher.
- Structured Professional Judgment (SPJ)
- Assessment approach that anchors clinical judgment to empirically validated risk-factor items while preserving room for case-specific integration.
- Validity
- The degree to which evidence and theory support the interpretation of test scores for a specific purpose; modern standards treat it as...