fix(experiments): Calculate win probability against control #27804
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andehen
reviewed
Jan 23, 2025
| - The first element is the probability that the control variant is the best | ||
| - Subsequent elements are the probabilities that each test variant is the best | ||
| A list of probabilities where each element represents: | ||
| - index 0: probability control variant beats all test variants |
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Yeah, control is a little tricky for this new behavior. Take this example:
- control and two variants, all equally good
- each variant will have a 50% chance to win (50/50 to beat control)
- control will only get a 33% chance to beat both variants.
So one can no longer compare these values then. Control will look worse than it is.
What I suggest we do, is that we for control show the probability to beat the best variant. I think that will be more meaningful to the user. And maybe update the description to say "Probability to beat control" and "Probability to beat best variant", respectively.
Alternatively, we could also drop showing this value for control.
andehen
approved these changes
Jan 23, 2025
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Size Change: 0 B Total Size: 1.16 MB ℹ️ View Unchanged
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See #26713
See https://posthog.slack.com/archives/C07PXH2GTGV/p1737374020186379
Changes
Switches all three win probability calculations to calculate the win probability solely against the control, instead of absolute win probability. Docs update: PostHog/posthog.com#10437
Tests document the difference between v1 and v2 behavior.
How did you test this code?
Tests should pass.