Underperforming ad: how I did the post-mortem

It happened to me recently while analyzing a campaign that started well and then dropped. The specific problem was that the team blamed the algorithm, but we didn't know if CTR, conversion, or CPM was dropping. At first, it seemed like just another case, but in production or in front of the client, those details get expensive very quickly. I didn't want to jump straight to the quick fix. I…