One method for calculating the validity of a screening instrument which takes into account ASD prevalence is Bayes Theorem.
To verify the method's potential use as an early warning system for human risk, we calculated the validity of the model-estimated risk map versus the raw incidence map from August 13 for predicting the case distribution for October 1, 2003.
If you wanted to, for instance, you could calculate the predictive validity of prowess at Scrabble, or the number of books a student reads in his senior year, or, more obviously, high-school grades.
And we used a paired t-test to calculate the discriminant validity.
Future studies should devote more effort to the follow-up of screen-negative cases to calculate the true validity indices in that specific sample, though it should be noted that following up such cases could be expensive since a majority may prove to be genuinely screen negative [ 44].
We also calculated the concomitant validity by considering only the questionnaires with complete data at T1 and T2 and obtained similar results (N = 66 (r = 0.45, 95% CI: 0.23 - 0.62, p < 0.01) and at T2 (r = 0.54, 95% CI: 0.34 - 0.69, p < 0.01).
