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Bayes effect size delta

HannahRapHannahRap Posts: 2
edited September 10 in JASP & BayesFactor

Hi there,

Two questions about the effect size used in JASP:

  1. What is an effect size (delta)? Is it Glass's delta?
  2. How do you convert Cohen's d into delta? (this is straightforward if delta is Glass's delta)



PS. Thank you Team JASP - the program is fantastic!!


  • EJEJ Posts: 368

    Hi Hannah,
    I assume you are talking about the t-test. Delta is the population version of the sample Cohen's d. So it is just the mean population difference divided by the population sd. You can find a detailed description in http://www.ejwagenmakers.com/2016/LyEtAl2016JMP.pdf (and also in the PBR t-test paper by Rouder et al., which is cited in the Ly paper).

    Thanked by 1HannahRap
  • Very helpful - thank you! And thanks for your speedy reply! Much appreciated:)

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