Hello everyone! I hope this is an appropriate place to ask my question. I am a 2nd-year PharmD student who is currently in my first Evidence-Based Medicine class (aka journal club).

We are having an exam next week, and I really wanted to make sure to start brushing up on the things we've learned about so far. So, yesterday I was looking at some research studies on PubMed and trying to review key concepts.

One topic I have been trying to improve my knowledge of is effect size calculations, like Number Needed to Treat/Harm and Cohen's d.

I had thought I was getting a decent grasp on how to calculate these and when to use each one, but then I ran across a study where the primary outcome was the change in occurrences of a certain disease event (I will just refer to this disease event as "episodes," for brevity's sake) from baseline to the end of the study.

So, the results were posted as follows: The intervention treatment group had a change in occurrences of the episode of -25 (that is, they experienced an…