Your question is Retention Change vs Seasonality. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You launched a retention-facing change on a Meta surface such as Instagram Reels or Facebook Groups, and retention moved right after launch. The same period overlaps with known seasonal traffic patterns, so a simple before-after read is not enough.
How would you diagnose whether a launch caused a change in retention versus a seasonal effect?