Effect size calculations

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prasadkrec
Posts: 2
Joined: Tue Aug 28, 2018 1:00 pm

Effect size calculations

Post by prasadkrec »

Hi

I am a naive use of JAMOVI. I tried to calculate the effect size for a paired t-test using JAMOVI. I checked the cohen's d using MOTE package and these numbers are quite different. Below is the code that replicates my output:

library(jmv)
data('bugs', package = 'jmv')
jmv::ttestPS(bugs, pairs = list(list(i1 = 'LDLF', i2 = 'LDHF')), hypothesis = "twoGreater", meanDiff = TRUE, effectSize = TRUE, ci = TRUE, desc = TRUE, plots = FALSE)

OUTPUT SHOWS cohen's d= -0.697

library(MOTE)
d.dep.t.avg(m1 =5.72 , m2 = 7.38, sd1 = 2.71, sd2 = 2.52 , n = 91, a = .05)

OUTPUT SHOWS cohen's d= -0.6347992

This not so much a rounding errors. Kindly advise

Cheers
Prasad
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jonathon
Posts: 2613
Joined: Fri Jan 27, 2017 10:04 am

Re: Effect size calculations

Post by jonathon »

hi prasad,

the sd1 of 2.71 looks to be based on the full 93 observations of LDLF, however LDHF has two missing values, and so these two cases need to excluded from LDLF as well.

if i take the sd1 value of 2.67 from the t-test descriptives, i get the same results.

(for the record MOTE is a *super-rough* package at this stage - i had to roll back a few commits to find a version which worked. maybe pick a package that's at least on CRAN next time :) )
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prasadkrec
Posts: 2
Joined: Tue Aug 28, 2018 1:00 pm

Re: Effect size calculations

Post by prasadkrec »

Hi Jonathon

Thank you so much for sharing this detail. Much helpful!

Warm Regards,
Prasad
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