Unclear how Win Probability is calculated

[jurajmajerik]

Feature request

Is your feature request related to a problem?

Our sharp-eyed analysts and PMs also have doubts about how Win probability is determined and there isn’t clear documentation (based on what I could find)

Describe the solution you'd like

Tooltip/link from the experiment results to the "Under the hood" docs

Describe alternatives you've considered

Additional context

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]