Effect Sizes and the Disattenuation of Correlation and Regression Coefficients: Lessons from Educational Psychology. - Practical Assessment, Research & Evaluation

The nature of social science research means that many variables we are interested in are also difficult to measure, making measurement error a particular concern. In simple correlation and regression, unreliable measurement causes relationships to be under-estimated increasing the risk of Type II errors. In the case of multiple regression or partial correlation, effect sizes of other variables can be over-estimated if the covariate is not reliably measured, as the full effect of the covariate(s) would not be removed.