Worked Walkthrough: A Back-of-Envelope Power Plan
Use a simple power-planning walkthrough to test whether the proposed runtime can answer the actual business question.
The PM wants a seven-day answer, but traffic is limited and the business would act on a moderate effect, not only on a huge one. Power planning is a tradeoff between meaningful effect size, available observations, and runtime. Teams often keep the deadline fixed and pretend the evidence will still answer the smaller-effect question they actually care about. Step 1 State the baseline and meaningful lift: current week-four retention is 12%, and the smallest worthwhile lift is 1 point. Without a decision-relevant effect, there is no honest power conversation. Step 2 Compare available weekly users to the information needed for…
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