How to Calculate Effect Sizes from Published Research: A Simplified SpreadsheetBy Will Thalheimer and Samantha Cook

Note: This spreadsheet follows the same outline as the article by Thalheimer and Cook (2002). How to Calculate Effect Sizes from Published Research: A Simplified Methodology

Updated April 2003 to deal more effectively with situations where the treatment-group mean is lower than the comparison-group mean.

TABLE OF CONTENTS

Subjects Mean Standard Deviation

Treatment Condition 25 100 100 Input Appropriate NumbersComparison Condition 25 400 75 in the cells to the left!!

3.46 huge effect Relative Size of Cohen's dnegligible effect (>= -0.15 and <.15)

numerator -300 small effect (>=.15 and <.40)den's num 1st 240000 medium effect (>=.40 and <.75)den's num 2nd 135000 large effect (>=.75 and <1.10)den's denominator 50 very large effect (>=1.10 and <1.45)den's total (s pooled) 86.6025403784439 huge effect >1.45

Percent Change Relative Size of % Change(From Comparison to Treatment) -75

huge decrease huge decrease <-75very large decrease (<=-50 and >-75)large decrease (<=-30 and >-50)medium decrease (<=-15 and >-30)small decrease (<=-5 and >-15)negligible change (>= -5 and <5)small increase (>=5 and <15)medium increase (>=15 and <30)large increase (>=30 and <50)very large increase (>=50 and <75)huge increase >75

Sheet 1 -- Calculating Cohen's d from t-testSheet 2 -- Calculating Cohen's d from t-test when you don't have Standard Deviations or Standard ErrorsSheet 3 -- Calculating Cohen's d from t-test when you have Standard Errors instead of Standard Deviations

Sheet 4 -- Calculating Cohen's d from F-testSheet 5 -- Calculating Cohen's d from F-test when you don't have MSE's

Sheet 1 -- Calculating Cohen's d from t-tests

Cohen's d

d=x̄ t− x̄c

√ (nt−1 )st2+ (nc−1 )sc2

nt+ nc

TABLE OF CONTENTS

when you don't have Standard Deviations or Standard Errors

Subjects

Treatment Condition 230 4.731 Input Appropriate NumbersComparison Condition 230 in the cells to the left!!

0.44 medium effect Relative Size of Cohen's dnegligible effect (>= -0.15 and <.15)

1st numerator 460 small effect (>=.15 and <.40)1st denominator 52900 medium effect (>=.40 and <.75)2nd numerator 460 large effect (>=.75 and <1.10)2nd denominator 458 very large effect (>=1.10 and <1.45)Within Square Root 0.0934538627031996 huge effect >1.45

Sheet 1 -- Calculating Cohen's d from t-testSheet 2 -- Calculating Cohen's d from t-test when you don't have Standard Deviations or Standard ErrorsSheet 3 -- Calculating Cohen's d from t-test when you have Standard Errors instead of Standard Deviations

Sheet 4 -- Calculating Cohen's d from F-testSheet 5 -- Calculating Cohen's d from F-test when you don't have MSE's

Sheet 2 -- Calculating Cohen's d from t-tests

t statistic

Cohen's d

d = t √ ( nt + ncnt nc ) ( nt + ncnt + nc −2 )

TABLE OF CONTENTS

when you have Standard Errors instead of Standard Deviations

Subjects Mean Standard Errors

Treatment Condition 24 57 0.226 Input Appropriate NumbersComparison Condition 24 53 0.272 in the cells to the left!!

3.34 huge effect Relative Size of Cohen's dnegligible effect (>= -0.15 and <.15)

numerator 4 small effect (>=.15 and <.40)den's num 1st 28.193952 medium effect (>=.40 and <.75)den's num 2nd 40.839168 large effect (>=.75 and <1.10)den's denominator 48 very large effect (>=1.10 and <1.45)den's total (s pooled) 1.19924559619788 huge effect >1.45

Percent Change negligible change Relative Size of % Change(From Comparison to Treatment) 8

huge decrease <-75very large decrease (<=-50 and >-75)large decrease (<=-30 and >-50)medium decrease (<=-15 and >-30)small decrease (<=-5 and >-15)negligible change (>= -5 and <5)small increase (>=5 and <15)medium increase (>=15 and <30)large increase (>=30 and <50)very large increase (>=50 and <75)huge increase >75

Sheet 1 -- Calculating Cohen's d from t-testSheet 2 -- Calculating Cohen's d from t-test when you don't have Standard Deviations or Standard ErrorsSheet 3 -- Calculating Cohen's d from t-test when you have Standard Errors instead of Standard Deviations

Sheet 4 -- Calculating Cohen's d from F-testSheet 5 -- Calculating Cohen's d from F-test when you don't have MSE's

Sheet 3 -- Calculating Cohen's d from t-tests

Cohen's d

d=x̄t− x̄c

√ (nt−1 )(SEt √nt )2+ (nc−1)(SEc √n c )2nt+ nc

TABLE OF CONTENTS

Subjects Mean MSE

Treatment Condition 48 1.69 2.34 Input Appropriate NumbersComparison Condition 48 4.64 in the cells to the left!!

1.95 huge effect Relative Size of Cohen's dnegligible effect (>= -0.15 and <.15)

numerator -2.95 small effect (>=.15 and <.40)den's numerator 94 medium effect (>=.40 and <.75)den's denominator 96 large effect (>=.75 and <1.10)denominator total 1.51368755032206 very large effect (>=1.10 and <1.45)

huge effect >1.45

Percent Change negligible change Relative Size of % Change(From Comparison to Treatment) -64

huge decrease <-75very large decrease (<=-50 and >-75)large decrease (<=-30 and >-50)medium decrease (<=-15 and >-30)small decrease (<=-5 and >-15)negligible change (>= -5 and <5)small increase (>=5 and <15)medium increase (>=15 and <30)large increase (>=30 and <50)very large increase (>=50 and <75)huge increase >75

Sheet 1 -- Calculating Cohen's d from t-testSheet 2 -- Calculating Cohen's d from t-test when you don't have Standard Deviations or Standard ErrorsSheet 3 -- Calculating Cohen's d from t-test when you have Standard Errors instead of Standard Deviations

Sheet 4 -- Calculating Cohen's d from F-testSheet 5 -- Calculating Cohen's d from F-test when you don't have MSE's

Sheet 4 -- Calculating Cohen's d from F-tests

Cohen's d

d=x̄ t− x̄c

√MSE ( nt+nc−2nt+nc )

TABLE OF CONTENTS

when you don't have MSE

Subjects F statistic

Treatment Condition 22 8.39 Input Appropriate NumbersComparison Condition 33 in the cells to the left!!

0.81 large effect Relative Size of Cohen's dnegligible effect (>= -0.15 and <.15)

1st numerator 55 small effect (>=.15 and <.40)1st denominator 726 medium effect (>=.40 and <.75)2nd numerator 55 large effect (>=.75 and <1.10)2nd denominator 53 very large effect (>=1.10 and <1.45)Within Square Root 0.812152199386638 huge effect >1.45

Sheet 1 -- Calculating Cohen's d from t-testSheet 2 -- Calculating Cohen's d from t-test when you don't have Standard Deviations or Standard ErrorsSheet 3 -- Calculating Cohen's d from t-test when you have Standard Errors instead of Standard Deviations

Sheet 4 -- Calculating Cohen's d from F-testSheet 5 -- Calculating Cohen's d from F-test when you don't have MSE's

Sheet 5 -- Calculating Cohen's d from F-tests

Cohen's d

d = √F ( nt + ncnt nc ) ( nt + ncnt + nc −2 )