"Can You Sum This Metric Across Dimensions?"

The Three Classifications What They're Really Testing The 60-Second Framework Step 4 is the strong-hire signal. Saying 'I would not store conversion_rate in the fact table; I would store clicks and impressions, and let the BI tool compute the ratio' shows you design for correct aggregation, not just convenience. Why Companies Care Cite these in your answer: 'At a major bank, a dashboard SUMmed daily balances across a month. The result was 30x the actual balance. The CFO reported it to the board before anyone caught it.' And: 'At an e-commerce company, pre-computed average order value produced mathematically wrong results when filtered by category because average-of-averages is not the same as the true average.' These stories prove additivity bugs are real and expensive.