If you want to run multiple A/B tests that have the same KPI and will have the same audience, you need to set up collision prevention so these projects do not collide and therefore corrupt your data.
You need to do this before you start any of the projects. The first thing you need to do is set the traffic allocation for each project.
Projects are evaluated in the creation order. So you need to set traffic allocation to lower than 100% (total) in the first project to be able to send some of the traffic to the other project. Notice that for the second project you want the total traffic allocation to be 100% because you want 100% of the 50% the first project leaves behind to be allocated to the second project.
In the example below we want to run two projects at the same time;
First, open the editor for project 1 (created first of the two). Then click on the Settings button. Choose Traffic allocation.
Then set the traffic allocation for the variants. If you wish the two projects to have equal traffic you want this setting to be a total of 50% in the first project.
Then open Audience settings and add a Collision prevention statement.
Now select the project you wish to set up collision prevention against in the dropdown. In this example that is the one named test 2. Hit Apply & Close to confirm this and then Save your Audience. Ok, now the setup for the first project (named test 1) is done.
Now we need to set up collision prevention for the second project (named test 2 in this example). We do that in the same way but here we choose the first project (test 1) in the collision prevention statement dropdown.
Remember to set the traffic allocation for the variants. If you wish the two projects to have equal traffic you want this setting to be a total of 50%, as in the first project.