I have a medical research in which I have two sets of data
- Control group: People who have no ailment.
- Study group: People who have some particular ailment.
Within each category there are subgroups like age, gender, blood pressure ranges, cholesterol ranges, etc.
Now I got a few observations (around 50) for both control group and study group. I have observation of various parameter like blood pressure, cholesterol level etc. I want to prove statistical significance of these parameter (Blood pressure/cholesterol) in study group. What is the best way to do it? Should i use $t$ distribution or normal distribution?
Also when I calculate the $p$-value, should I compare each subgroup in study group (based on range) with corresponding subgroup in control group or calculate $p$-value as a whole for study vs control group?