# Statistical Test for Many different groups before and after an Event?

I have 200 species of animals and I want to check whether giving them a medicine can affect them in a significant way. I study 20 days before administering the medicine and 20 days after, such that an example of my data is as follows:

Species     |    Date     |     Value
A        |    ....     |      4
A        |    ....     |      10
...            ....           ...
B        |    ....     |      50


etc.

I know that by using a two-way t-test for each individual species I can determine whether the medicine had any effect by comparing the 20 days before to the 20 days after, but since I have 200 species it means I have to run 200 separate two-way t-tests, so I was wondering whether there is a one single statistical test which can determine whether the medicine had a significant effect. I thought about using something like an ANOVA test but that doesn't seem appropriate (or at least what I found online doesn't seem to support it) so I thought I should ask here to find out what I can do. Thanks!

• A linear (mixed effects) model, if you examined the same animal before and after. If you have two different animals for before and after, a regular linear model. Commented Sep 16, 2019 at 6:41