Positive predictive power tends to be low for rare diseases. Multiple regression analysis and incremental validity. Multiple and semi-partial correlation. Commonality and its problems. Partial regression and partial correlation.
Stepwise regression is hypersensitive.
Prediction of academic performance at Penn from SAT, achievement tests, and class rank. Prediction may be almost as good with non-optimal as with optimal regression weights. Factor analysis and construct validity. Single factor and multi-factor conceptions of intelligence. Differences between common factor analysis and principal components.