Your question is Regression Forecast for Campaign Impact. 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 are reviewing a paid campaign that ran for 8 weeks. Weekly sign-ups were already trending up before launch, and you want to estimate how much of the post-launch lift is explained by the campaign versus the existing trend.
How would you use a simple regression or forecasting model to estimate campaign impact?