I'm stuck trying to find a way to compare whether or not a given intervention has a greater effect in one group (Kids < 5) than another group (Kids > 5). The outcome I'm comparing is the incidence of diarrhea in children receiving probiotics compared to controls. It is a meta-analysis involving 11 studies and I have decided to specify several subgroups to compare (eg. studies with reported mean ages < 5 and those with mean ages > 5).
Both groups show a statistically significant reduction in incidence between treatment and control. There is also a statistically significant difference in the incidence between the two treatment groups (as well as control groups). Ie. the incidence of diarrhea is higher in studies reporting mean age < 5 years.
I used MedCalc Meta-analysis: Proportions to find pooled rates then used chi-square test for equality of proportions to compare.
What I want to know and can't figure out is whether or not probiotics are more effective when used in the higher risk group compared to when their used in the lower risk group.
Thanks for any and all help, I'm truly stuck on this one.