Question
9. Effect size- Cohen's d and r squared An industrialyorganizational psychobgist has been consubg "th acompemy that runs meekendSeeking workshcps for the unemployed. She collected dota on several issues reliated to these workshops and, at ler conducting statistical tests, obtained stetistically significent findings she needs to find a way to evaluate efflect sue so thel she can make recommendations to the company One of the paychologist's indings is that 1s months after the workshop, a sample of 49 job seekers mho received training on using the internet to fied job istings scored an average of 6 5 95 measined on a 9-point job-pearch satisfaction scale, nth a standard devwiation of s.2. The typical job seeker scores s n ponts The psychologist finds that the estimated he's d “ . me t statstit 64,Lz, and r‘ using cohers d and conen's puidelines for interpreting the effect size weh the estmated Coben's d,there i& a treatment effect using r and the extension of Cohens gudelines for intergreting the effact treatmest effect Hint: when uang Cohens puidelines for interpreting the size using 2, there is effect size, fthe value les between tao categones, then speofy the rasge covered by both categenes, for example, medum to large Another oie of the psychalogists Bocings e that a smple o 144 job seekers who recelved training on nderview skils worked more than s0 ous 1 average ot 69 mortts in the lust year, iston a standerd deviatien of 25.Th typical ob seker sorks 64 moths the t stasctic e 2.38, and s using Conersd She fids that the mteated Cohems a s and cohens guiseines for interpreting the effict size wth the estinated Cahes d there is a treaemant eftest nd the eatension o cohens guudeiors for isterpreting
Explanation / Answer
Estimated Cohen'd = Mean difference / standard deviation = (6.5 - 5.8)/ 1.2 = 0.583
So, effect size is between medium (0.5) to large(0.8).
here t is given which is equal to 4.12
R2 = t2 / [n - 2 + t2 ] = 4.122 / (49 -2 + 4.122 ) = 0.2653
the effect size using R2 is large.
(b)
Estimated Cohen'd = Mean difference / standard deviation = (6.9 - 6.4)/ 2.5 = 0.2
So, effect size is Small(0.2)
here t is given which is equal to 2.38
R2 = t2 / [n - 2 + t2 ] = 2.382 / (144 -2 + 2.382 ) = 0.03835
the effect size using R2 is from small to medium
All these are as per guidlines of cohen's d and r2
