# ABStrips (/docs/charts/ab-strips)

ABStrips answers "did B beat A — and by more than the overlap?". It draws **two graded quantile strips on one shared
scale**: a faint p5–95 band, a stronger p25–75 middle half, and a median dot, with row A muted and row B accent. The
visible overlap of the two middle halves is the answer — and the overlap number is always in the summary, because an
average delta without its spread is how A/B results lie.

```tsx
<ABStrips
  data={{
    a: Array.from({ length: 80 }, (_, i) => 130 + ((i * 13) % 44) - 22),
    b: Array.from({ length: 80 }, (_, i) => 116 + ((i * 13) % 44) - 22),
  }}
  format={{ style: "unit", unit: "millisecond", unitDisplay: "short", maximumFractionDigits: 0 }}
  positive="down"
  title="Latency A/B"
  width={260}
  height={26}
/>
```

## Install

```tsx
import { ABStrips } from "@microcharts/react/ab-strips";

const control = Array.from({ length: 80 }, (_, i) => 130 + ((i * 13) % 44) - 22);
const test = Array.from({ length: 80 }, (_, i) => 116 + ((i * 13) % 44) - 22);

<ABStrips data={{ a: control, b: test }} positive="down" title="Latency A/B" />
```

Setup (package + stylesheet): [Quickstart](/docs/quickstart#set-up-with-an-ai-agent) or paste [`/agent-setup.md`](/agent-setup.md) into your agent.


## When to use it

- **Good for** — an A/B experiment result in a KPI card, control vs test in an experiments table, any two-sample
  comparison where the spread matters.
- **Avoid for** — a single distribution (BenchmarkStrip) or more than two arms (small multiples).


## Variants

```tsx
const control = Array.from({ length: 80 }, (_, i) => 130 + ((i * 13) % 44) - 22);
const test = Array.from({ length: 80 }, (_, i) => 116 + ((i * 13) % 44) - 22);

<ABStrips data={{ a: control, b: test }} seriesLabels={["Control", "Test"]} />
```

## Edge cases

```tsx
// an empty (or all-non-finite) arm renders no strips and announces "No data."
<ABStrips data={{ a: [], b: [110, 120, 130] }} />
```

```tsx
// fewer than 8 points in an arm: that row's outer band falls back to the
// observed min–max instead of p5–95 — tail quantiles are fiction at n < 8
<ABStrips data={{ a: [100, 130, 145], b: control80 }} />
```

Either arm with zero finite values makes the whole comparison unanswerable — no strips draw, and the accessible name
reads plainly **"No data."** rather than a comparison against nothing. An arm with fewer than 8 points still draws (a
small sample is still the honest sample you have); only its outer band changes meaning, from the 5th–95th percentile to
the plain min–max, because percentile estimates need more than a handful of points to mean anything.


## Why this default

Overlap in the summary, because an average delta without spread is how A/B results lie. The strips are mandatory context
— it never degrades to a bare mean bar — and the delta label never appears without the distributions behind it. When the
middle halves fully overlap the summary says "no clear difference"; when they're disjoint it says "clearly separated";
and an arm with fewer than 8 points falls back to a min–max band.

## Accessibility

The accessible name states both medians, the delta, and the overlap — **"Test median 115 ms vs Ctrl 129 ms (-11%);
middle halves overlap 35%."**. The interactive entry roves the rows (↑/↓) and the quantile edges (←/→): the median
announces the delta vs the other arm, other edges announce the percentile.

The interactive entry follows the shared [interaction contract](/docs/accessibility#one-interaction-contract):
arrow keys rove between units on both axes, `Home` and `End` jump to the ends, and a click, tap, `Enter` or
`Space` selects a unit — pinning its readout so it survives blur, until you select it again or press `Escape`.
On touch, a tap pins and a drag scrubs.

## Props

| Prop | Type | Description |
| --- | --- | --- |
| `data` (required) | `{ a: number[]; b: number[] }` | The two arms — raw samples, not summaries. |
| `seriesLabels` | `[string, string]` | Row identities for the gutter tags + summary (default ['A', 'B']). |
| `positive` | `"up" \| "down"` | Which direction of the B−A delta reads as good (colors the delta). |
| `label` | `"delta" \| "none"` | Signed median delta in a right gutter. |
| `animate` | `boolean` | (interactive) Opt-in entrance motion when the chart mounts client-side — add `import "@microcharts/react/motion"` once. Inert on the server, on hydrated server HTML, and under `prefers-reduced-motion`. |

Plus the shared grammar — `data`, `domain`, `color`, `title`, `summary`, `format` — and the layout props (`width`, `height`, `className`, `style`) that every chart accepts. Interactive entries also share `animate` and `live`, and — wherever a chart has more than one navigable unit — `onActive`, `onSelect`, `selectedIndex` and `defaultSelectedIndex`; and — wherever the chart shows a hover value — `readout`. See [the shared grammar](/docs/quickstart#the-shared-grammar).