I'm looking at clinical trial data where there are various numbers of patients on different arms (A, B, C, D). All arms receive a drug that is known to cause a toxicity, but some arms receive an additional drug which might contribute to the toxicity. I have been using 3 methods to identify the number of patients with the toxicity, and I was curious if the ratios of patients on the different arms differed between the methods and whether the ratios might have been higher on some arms (suggesting the additional toxicity of the added drug) than what is seen with the entire population.
For example, number of patients identified with the toxicity with the different methods:
A B C D Total method 1: 8 18 26 16 68 method 2: 45 111 53 113 322 method 3: 68 158 69 153 448 Overall: 695 1331 441 925 3392
To compare, I calculated the percentage of patients on each arm for each of the methods (Method 1 Arm A: 8/68) and compared it to the overall population (695/3392). However, after doing this, I was told I need to normalize by the patients on each arm. I am not sure what is meant by this. I can divide the numbers of patients identified for each arm by the total number of patients on the arm, but then how does this help me do the comparison I am interested in? I don't have a stats background, so I am not sure how to tackle this question in general.