Questions About Research

Ok so me, Ryan and Sams research project for Epidemiology has changed slightly and i was wondering if we need to change our IRRB submission, or even if we have to submit one at all.

Ryan has found a school that keeps tracks of their students height and weight. Also the school has gone from sugary snack food in vending machines to healthy snacks. We are planning to compare the weight of before sugary snacks to after they where removed.

Since all the data has been collected for us, we only have to really analyze it. Do we need IRRB permission to do that? and how do we need to set up our consent form?