feat(experiments): New running time calculator (1/2)

[jurajmajerik]

Feature flag: experiments-new-calculator

Problem

Our running time calculator sucks isn't great.

Changes

• Implemented a new calculator that uses existing experiment results as input.
• It looks at the first primary metric in the list and uses the same methods based on the metric type.
• It’s almost stateless - no kea logic, just a small local state for MDE, and pure functions for all estimations.

https://www.loom.com/share/96cce3083fa54eb7b3ad782ac0308e00

This is part 1 - automatic calculation based on results, which will be good enough for most users. Part 2 will add the option to calculate sample size using fully manual inputs (an “advanced” mode for experienced users).

How did you test this code?

Added unit tests for the new methods that replicate the kea logic tests of the existing calculator.

[greptile-apps]

_{10 files reviewed, 4 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

logic: baselineValue of 0 is a valid value (e.g., 0% conversion rate), but here it's treated as falsy and returns null

Suggested change

	if (!baselineValue) {
	return { currentExposures: null, recommendedSampleSize: null, exposureRate: null, estimatedRemainingDays: null }
	}
	if (baselineValue === null) {
	return { currentExposures: null, recommendedSampleSize: null, exposureRate: null, estimatedRemainingDays: null }
	}

Prompt To Fix With AI

This is a comment left during a code review.
Path: frontend/src/scenes/experiments/RunningTimeCalculatorNew/calculations.ts
Line: 264:266

Comment:
**logic:** `baselineValue` of 0 is a valid value (e.g., 0% conversion rate), but here it's treated as falsy and returns null

```suggestion
    if (baselineValue === null) {
        return { currentExposures: null, recommendedSampleSize: null, exposureRate: null, estimatedRemainingDays: null }
    }
```

How can I resolve this? If you propose a fix, please make it concise.

[github-actions]

Size Change: +56 B (0%)

Total Size: 3.43 MB

ℹ️ View Unchanged

Filename	Size	Change
frontend/dist/toolbar.js	3.43 MB	+56 B (0%)

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[rodrigoi]

This is a much better UX. A list of non-blocking things for now, or the future 😉 :

• Divisions by zero. This was a problem that plagued the old calculator. I would recommend adding checks and tests to calculations.ts.
• Modal Logic. Instead of adding to modalsLogic.ts, create a tiny logic to control the modal, like metricSourceModalLogic.tsx. Or search for *ModalLogic.ts in the codebase.
• Running time logic. For RunningTimeNew.tsx, add logic because you have an effect.