# Can Hedges' d be used to compare unlike effects?

I've got a question related to the use of Hedges' d in a meta-analysis of insect fitness information. Here is a link (pdf) to the paper I'm working with.

In the appendices, the fitness information is presented. Hedges' d is used to standardized the effect of multiple-mating (polyandry) on various fitness metrics across many different species. I am trying to compare the effects of polyandry in social insects on the effects of polyandry in nonsocial insects. The trouble seems to be, however, that very few studies investigate fitness in the same way in these two groups. Social insect fitness is usually measured in terms of parasite resistance or colony gender ratio, whereas nonsocial insect fitness is often measured by things like fertility, fecundity, adult body size, and other, somewhat simpler metrics.

So, my question is, can I compare the the Hedges' d for the effect of polyandry on nonsocial insect fecundity with the Hedges' d for the effect of polyandry on social insect parasite resistance? Would this be a meaningful comparison? Part of the data I'm working with is in the pictures below.

Here is a description from the methods section of the paper describing what they're doing:

"The common effect size we calculated was Hedges' d [i.e. J-corrected Hedges' g sensu Rosenberg, Adams & Gurevitch (2000); but note that Cooper, Hedges & Valentine (2009) refer to the J-corrected effect as Hedges' g]. We preferentially calculated Hedges' d using the mean and a measure of variance (standard deviation or error) for each treatment derived from individual female values. Means and measures of variance were extracted from summary tables, the text or figures (using Image J v. 1.43). Where this approach was not possible, we converted test statistics (t, F or χ2) or P values from tests of the main effect of the ‘number of mates’ treatment to Hedges' d using the software package MetaWin v. 2.0 (Rosenberg et al., 2000). We then calculated the variance using the number of females per treatment as the sample size. In a few cases only the total sample size was provided. If so, we set the sample size as equal across treatments."

Here is the social insect fitness information:

Here is (some of) the nonsocial insect fitness information:

• By "Hedges' d", do you mean Cohen's $d$ or Hedges' $g$? – gung Nov 11 '14 at 22:02
• It's L.V. Hedges being referred to, so the possessive could be Hedges' or Hedges's, but certainly not Hedge's. Edited accordingly. Whether the coefficient is his is a different question. – Nick Cox Nov 11 '14 at 22:06
• Tables are not readable at least by me on my machine. – Nick Cox Nov 11 '14 at 22:08
• @NickCox, if you right click -> view image, they get much bigger. – gung Nov 11 '14 at 22:11
• I just added some information in the bod the question regarding what they're actually calculating. – Max Nov 11 '14 at 22:13