A single estimate of separate within-individual correlations: applications in psychopharmacology.
Simple procedures are proposed to describe relationships between sets of repeated measures within study subjects. An example is the association between blood levels of prolactin and a drug (e.g., methylphenidate) measured at multiple time-points across study subjects. These procedures consist of (a) estimating Pearson product moment correlation coefficients (rs) within individuals using all the observations available per individual; (b) estimating an average r that pools the information across study subjects; (c) testing whether these rs are homogenous using a simple chi-square test; and (d) testing the average r for statistical significance. If these individual rs are found to be homogeneous, the average r is taken as representative of the individual rs. Testing rs for homogeneity and pooling them across individuals are relatively old procedures (Snedecor 1956). Recent applications can be found in the meta-analytic literature (Rosenthal 1983). Applications are demonstrated using actual data. We recommend using these procedures because they are simple and easily applied and interpreted.
Alvir
J M
JM
Hillside Hospital, Division of Long Island Jewish Medical Center, Glen Oaks, NY 11004.
Lieberman
J A
JA
Borenstein
M T
MT
D006801:Humans; D007206:Individuality; D011600:Psychopharmacology / Q000706:statistics & numerical data*; D012107:Research Design