(This is part-2 of my long question, you can have a look at part-1 here)
I am going to do a quasi-experiment, with measuring the base line of a sample (actually not quite a sample, but a ward, with high patient turn-over rate), and then we do a intervention, and measure the variables (i.e. infection rate) again.
I googled a bit and found that this is something called a single case experiment, and it was said that single case experiment doesn't have very solid statistics because you don't have the control, you can't conclude on the causality in a solid manner.
I have googled a bit again and found that I can compare the incidence rate (or call it infection rate), but doing something like "incidence rate difference" (IRD) or "incidence rate ratio" (IRR). (I found it from here)
What is the difference between IRD and t-test? And is there any statistical test complementary for IRR?
But mostly importantly, is it appropriate for me to use this test (does it have a name?) for single case experiment? Because the patients in the ward keep changing, this is what I worried about.