In this guide, Cohen’s f 2 was chosen as an appropriate measure of local effect size for variables within a multivariate, mixed-effects regression model. However, it is important to note caveats to this approach. First, some statisticians have objected to standardized effect size, as it can be reduced by variables with low reliability/high variance, and is unstable across studies with different designs, such that repeated-measures studies typically yield stronger effect sizes compared to an equivalent independent design (Baguley, 2009). Additionally, standardized effect size can be distorted by the sampling procedure (e.g., sampling from a truncated distribution, sampling from the tails of the distribution, or restricting to a subset of the population; Baguley, 2009), and thus generalizing standardized effect sizes should be done with caution.
