Effect Size - Statistics Solutions
https://www.statisticssolutions.com/.../effect-sizeTypes of effect size. Pearson r correlation: Pearson r correlation was developed by Karl Pearson, and it is most widely used in statistics. This parameter of effect size is denoted by r.The value of the effect size of Pearson r correlation varies between -1 to +1. According to Cohen (1988, 1992), the effect size is low if the value of r varies around 0.1, medium if r varies around 0.3, and ...