Let's say I have an app, and I need to request a permission from the user to use the main use case of the app. This permission request happens the first time that the user opens the app.
- Scenario A: I display a prompt "in-app", saying "We'll need this permission to do this and that", giving context and when the user clicks "OK", I show them the iOS prompt for the device permission.
- Scenario B: I display the iOS prompt directly on start-up.
I know that each mandatory prompt you display on first start will cause you to lose some users. My question is: are there scientific studies, or trustworthy results, who indicate how many are lost by each of the two options? Does scenario A lose more users because there are two prompts? If so, how many?
Note that I'm only interested in the user loss rate. This question is specifically not about good practices or user happiness.