I studied the impact of advertising for apps a few years ago and there was a similar effect: advertising reduced the decision time (which can be surprisingly lo

I studied the impact of advertising for apps a few years ago and there was a similar effect: advertising reduced the decision time (which can be surprisingly long, while 50% reacted within 24 hours, 20% did so more than 3 weeks later). If your analysis window is too short, you will mistake this effect for a genuine increase.