Attribution window
The period after seeing or clicking an ad during which a conversion is still credited to it.
What makes it wrong.
The mechanism, not the warning.
Windows also make recent data provisional. A report pulled today for yesterday is missing every conversion that will land inside the window over the coming days, so the last few days of any series are systematically understated and look like a decline.
In detail.
A seven-day click and one-day view window credits a purchase made six days after a click, and a purchase made the same day as a view. Widening the window increases attributed conversions without changing behaviour; narrowing it decreases them.
Because platforms default to different windows, comparing attributed results across platforms compares different definitions before it compares anything else.
Through an agent.
What changes when a model asks instead of a person.
Ask for the last seven days and a model reports a downward trend that is an artefact of the window. Comparable series need the tail excluded, or the same lag applied to both periods.