I performed propensity score matching and thus generated a quasi-randomized study.
Now I got a risk for Akute Kidney Injury of
Drug1: 15.6 % Drug 2: 11.2 % Sample size = 4711 control + 4711 treated
I also tested for renal replacement therapy and got Drug 1: 6.6 % Drug 2: 6.2 %
and mortality Drug 1: 6.5 % Drug 2: 6.3 %
Now intuitively, the risk difference in renal replacement and mortality is NOT statistically significant, but the risk for AKI is.
My question is this: Which statistical test should I use to determine if the difference is statistically significant? Would a simple t.test suffice considering I calculated the risks using the mean()-function, but the risk is not "really" a mean on a ratio scale?