I have three groups with two hundred individuals each, and each individual withtin a group has a pre and post treatment measurement. A single groups contains individuals with similar pre measurement scores.

If I wanted to see which groups have had a significant change in their measurements from pre to post treatment, what statistical test should I use?

Thank you for your help.

I have three groups with two hundred individuals each, and each individual within a group has a pre and post treatment measurement. A single group contains individuals with similar pre measurement scores.

If I wanted to see which groups have had a significant change in their measurements from pre to post treatment, what statistical test should I use?