Timeline for Effect size in contrast analysis
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 27, 2013 at 8:29 | vote | accept | adelweis | ||
| Jan 30, 2013 at 10:05 | history | edited | russellpierce | CC BY-SA 3.0 |
added 2 characters in body
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| Jan 30, 2013 at 10:03 | comment | added | russellpierce | AFIK, your only other mainstream options are to aggregate your data for the desired comparisons, run it back through the ANOVA machinery to yield a partial eta or partial omega or to convert your t to an r. However, my money is on all three of the above yielding the same number since k = 2. | |
| Jan 30, 2013 at 10:02 | comment | added | russellpierce | That part I am sure about. Your individual contrasts are just paired samples t-tests. Paired samples t-tests are just one sample t-tests of difference scores (against $\mu = 0$). The cohen's d formula for one-sample tests is applicable. That the numerator is a difference score takes into account the dependence/correlation/relatedness of the measures. | |
| Jan 30, 2013 at 6:30 | comment | added | adelweis | Thanks for your help. This is actually the only thing that seems to me reasonable. However I'm still not sure if using Cohen's d here is a valid approach. | |
| Jan 30, 2013 at 5:36 | comment | added | russellpierce | If you wait around a few hours, I'm sure you'll get more skilled and authoritative help than me. | |
| Jan 30, 2013 at 5:35 | comment | added | russellpierce | However, since you are using MSe, I think what you would do is use $\sqrt{MSe}$ as your estimate of $s_{d}$. I tried to spot check my intuition but ezANOVA doesn't like yielding its tasty source table secrets for within subjects designs. Since you have the values in front of you, you can do a quick sanity check on the procedure by comparing $s_{d}$ calculations with non-GG adjusted $\sqrt{MSe}$ values. To the extent the assumption of sphericity is correct, these values should be similar. For your actual calculation you would... I guess... use the GG corrected $MS_{error}$. | |
| Jan 30, 2013 at 5:33 | comment | added | russellpierce | You can't use the between subjects variance in each of those cells. It doesn't match the test you are doing. You could use the SD of the differences (difference scores) between the two cells... but only if your contrast was actually calculated as a paired samples t-test using the standard deviation of differences as your error term. | |
| Jan 30, 2013 at 4:37 | comment | added | adelweis | Do you mean that even though I'm using MSe from 2-way ANOVA to calculate contrasts, when calculating Effect Size I can use SD between two cells instead? | |
| Jan 30, 2013 at 4:16 | history | answered | russellpierce | CC BY-SA 3.0 |