Decision window
How many days of evidence a decision uses. Longer is more reliable, shorter is more current.
The core trade-off in all of advertising analysis. Long windows are statistically sound and slow to notice change. Short windows react quickly and mistake noise for signal.
AutoPPC sets it per marketplace, because a thinner marketplace needs longer to accumulate the same confidence. Amazon's search-term lookback caps near 95 days.
One rule matters more than the length: the window should start after the last significant change — a deal, a stock-out, a restructure, a prior optimization.