As mentioned previously, the other source of error is range departure.
This is the random deviation from rho (the estimated population mean effect
size) because of variation due to the
restriction,
(when selecting a decreased range of scores) or inflation (when selecting
extreme scores only) of the range of possible scores on any measure.
To
correct for range departure, first compute the ratio of the standard
deviation of the individual study
to the standard deviation of some reference population, "u". This ratio
is used to construct "c", an estimate of the range departure for the individual
study that presents the standard
deviation information. The formula for calculating c is
presented below:
