PERCEPTION OF PEARSON PRODUCT MOMENT CORRELATIONS FROM BIVARIATE SCATTERPLOTS

Perceptions about the Pearson product moment correlation, r, from bivariate scatterplots were investigated through the use of a questionnaire. It was found that subjects who are relatively sophisticated in psychometric techniques tend to underestimate the magnitude of r, with most pronounced disparity in the range .2 < |r| &lt .6. Additionally, estimates of r from specially designed scatterplots indicated that subjects (1) correctly estimated the effects of range restriction, (2) underestimated the effects of attenuating outliers, (3) incorrectly reduced estimates of r when the regression slope was relatively high or low, and (4) often failed to consider the effects of removing the middle third of the data. Several implications of these generally conservative estimations are discussed. Copyright © 1979, Wiley Blackwell. All rights reserved