> For the complete documentation index, see [llms.txt](https://seekspeed.gitbook.io/seekspeed-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://seekspeed.gitbook.io/seekspeed-docs/reports/ab-comparisons.md).

# A/B Comparisons

A report with **exactly two** runs unlocks the A/B comparison view. It overlays:

* Side-by-side TTFT and total latency distributions (violin plots).
* Per-prompt deltas (variant − baseline) ordered by magnitude.
* Welch's *t*-test on each metric (TTFT, total, throughput) with a significance badge.
* Cost delta in USD across the whole set.

## Interpreting the badge

| Badge                          | Meaning                                                              |
| ------------------------------ | -------------------------------------------------------------------- |
| 🟢 **Significant improvement** | `p < 0.05` and mean moved in the desired direction. Safe to promote. |
| 🟡 **Suggestive**              | `0.05 ≤ p < 0.10`. Re-run with more iterations before deciding.      |
| ⚪ **No effect detected**       | `p ≥ 0.10`. Treat as no change.                                      |
| 🔴 **Significant regression**  | `p < 0.05` in the wrong direction. Do not promote.                   |

The "promote variant" action on an A/B report is only enabled for 🟢 results that also pass the [accept gate](/seekspeed-docs/optimization-engine/apply-measure-accept.md).


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