Set decision date
The decision date is when you stop watching and decide what to do.
Without a decision date, an experiment can stay open forever. That makes it less useful. The goal is not to collect endless data. The goal is to learn enough to choose the next step.
Date the test must resolve
Pick a review date that fits the test.
If the experiment is tied to prompt movement, wait for enough prompt runs. If it is tied to a page launch, wait until the page has had time to be found and read.
Set the review date
Choose when the test should be read.
Freeze the main change
Avoid changing the test halfway through.
Read the window
Compare before and after data.
Make the call
Ship, adjust, or abandon the change.
Data before start
The before window should be known before the decision date.
If you do not know what the earlier state looked like, the later decision will be weaker.
Measurement effect
A decision date protects the team from endless review.
It also helps CLEA schedule the right follow-up task. The task can ask for a decision note instead of another vague summary.