Effect Size FAQs

  • Why does my research methods textbook have no entry for “effect size”?

    Because it’s a bad textbook! Most textbooks are about 20-30 years behind the state of the methodological art. Prior to writing The Essential Guide to Effect Sizes I scanned more than 30 texts published between 2000 and 2009. I found that 9 out of 10 had nothing to say about effect sizes. If effect sizes…

    Paul Ellis