I'm conducting biological experiments and have to normalize my raw data to the value of the untreated control in order to analyze them. This means that I have for the untreated sample something like {1,1,1,1,1} and for the treated sample something like {1.12,2.1,2.05,1.85,1.78}. How do I test if both sets are significantly different? I obviously cannot enter 1,1,1,1,1 into a t-test, can I?
In case I want to test for a significant difference in two treated samples, lets say treated with two different doses which have, on their own, also been normalized to the untreated control (Dataset A {1.12,2.1,2.05,1.85,1.78}, Dataset B {2.2,3.1,2.5,2.9,1.8}), how do I do this the right way?
Thanks a lot!
Best Answer
Actually, you can. In fact, entering all 1's for one group is equivalent to testing whether the treated group has a mean of 1. E.g. in R
the two t tests give identical results.
However, the second version seems, somehow, 'cleaner' - perhaps less likely to raise eyebrows or demand clarification.