Common cause

Ask whether some third thing upstream produced both the suspect and the result, so the two only look linked. If it did, killing your suspect changes nothing, because the real driver sits behind it and drives the outcome on its own.

Ask whether some third thing upstream produced both the suspect and the result, so the two only look linked. If it did, killing your suspect changes nothing, because the real driver sits behind it and drives the outcome on its own.

Example

In the shop case: your supplier raised wholesale costs 18 percent in July. That forced your price increase and also cut your ad spend, which drained traffic. Price and sales moved together, but the supplier hike caused both, so rolling prices back would not recover the sales.