This study empirically investigated equations for
estimating the value of the multiple correlation coefficient
in the population underlying a sample and
the value of the population validity coefficient of a
sample regression equation. In addition to previously
published estimation equations, several new
procedures, including an empirically derived equation,
were evaluated using 16 independent populations.
Overall, the empirical equation was superior
to any of the previously published estimation procedures.
It appears that cross-validation may no
longer be necessary for certain purposes.