I have performed a Cochran's Q test for a within-subjects experimental design with 3 conditions and 36 participants with a dichotomous dependent variable.
I found a (just) statistically significant effect ($\chi^2$ = 6.00, df = 2, p = 0.04979) and would like to also report the effect size, but haven't been able to find any information as to which effect measure to use and how to calculate it.
Any pointers would be gratefully received - the domain is human factors (psychology).