Age-adjusted General Intelligence
I am learning about Spearman's (1904) General Intelligence. I have turned to JASP to try and understand what is the first example of Factor Analysis, but the method used in JASP is not the same as in Spearman's paper. JASP defines "Residuals" as "residuals [of a variable] after regressing it on Age", however nowhere does Spearman mention "residual" or "residuals". No formula is furnished. Columns simply appear under "Residuals this" and "Residuals that" to 8 decimal places without so much of a calculation.
Please explain how I should go about calculating a residual [of a variable] after regressing it on Age for each subject.