We’ve just learned how to calculate the purchase rate based on all signups within a period of time. It already gave us so much – we can monitor the purchase rate over time and better understand our product and marketing efforts (ideally purchase rate doesn’t drop and goes only higher).
The only problem is that the purchase rate based on all signups doesn’t really help us learn. Imagine you have 2 marketing campaigns – one great (high purchase rate) and one really bad (low purchase rate). Ideally, we’d compare the purchase rate for users in each...