My guess is if they did t-tests or ANOVA it was on the rates, not counts. Validity of that is debatable but the numbers are large enough to not cause too much concern on my part.    One thing, NEVER assume that the analysis used is appropriate and what you should be doing, make the decision based on your data and statistical knowledge, you have to be able to defend it and there's too many studies that demonstrate statistical issues these days.  ... View more