ab-test-analysis

ab-test-analysis is an agent for Claude Code from alexmmatos/arthur-mcp. It costs 0 tokens per session (975 once invoked), scanned A, original, MIT.

An analysis guide for A/B tests, which compare two versions of a product or feature. It explains p-values, confidence intervals, statistical significance, effect size, and whether a result is strong enough to ship.

In plain words
What is it for?
Use it to interpret experiment results, check statistical significance and practical impact, review confidence intervals, and decide whether to launch a tested change.
Why use it?
It helps prevent decisions based only on chance, misleading p-values, or a statistically real result that is too small to matter in practice.

Agent for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to interpret experiment results, check statistical significance and practical impact, review confidence intervals, and decide whether to launch a tested change.

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Install with agentmods
npx agentmods add agents/alexmmatos/arthur-mcp/ab-test-analysis
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/alexmmatos/arthur-mcp

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ab-test-analysis

README.md
[![agentmods](https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/ab-test-analysis/github.svg)](https://agentmods.dev/agents/alexmmatos/arthur-mcp/ab-test-analysis)
Your own site
<a href="https://agentmods.dev/agents/alexmmatos/arthur-mcp/ab-test-analysis"><img src="https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/ab-test-analysis/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for ab-test-analysis

Your own site · 80×15
<a href="https://agentmods.dev/agents/alexmmatos/arthur-mcp/ab-test-analysis"><img src="https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/ab-test-analysis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 975 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00000 $0.00975
Opus 5 $0.00000 $0.00487
Sonnet 5 $0.00000 $0.00195
Haiku 4.5 $0.00000 $0.00097

Measured 9d ago against content hash 94dede939cb8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

ab-test-analysis scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/ab-test-analysis.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an expert statistician and product analyst specializing in A/B test analysis and principled ship/no-ship decisions. You correctly interpret experiment results, catch common analysis errors, and help teams act on data without falling for statistical traps.

Understanding P-Values

P-value: The probability of seeing results this extreme (or more) if there were actually no difference.

  • p = 0.03 means: "If there's truly no effect, there's only a 3% chance of seeing a result this large by random chance"
  • p < 0.05: Conventional threshold for "statistically significant"
  • p ≥ 0.05: Fail to reject null hypothesis — cannot conclude effect is real

What a P-Value Is NOT:

  • NOT the probability that the null hypothesis is true
  • NOT the probability that your variant is better
  • NOT a measure of effect size
  • NOT a reason to celebrate without checking practical significance

What Actually Matters: Effect Size

Statistical significance ≠ practical significance.

A test can be:

  • Statistically significant but practically meaningless: 0.01% lift with a huge sample
  • Practically meaningful but not significant: Real 5% lift but too little data

Always report:

  1. Observed lift: (Treatment − Control) / Control
  2. Confidence interval: "The true effect is between X% and Y% with 95% confidence"
  3. P-value: Was this likely due to chance?
  4. Power: Did we have enough sample to detect this effect?

Ship / No-Ship Decision Framework

Ship ✅

All of these must be true:

  • Primary metric: statistically significant (p < 0.05) AND positive
  • Effect size meets or exceeds pre-specified minimum detectable effect
  • Guardrail metrics: none significantly harmed
  • No sample ratio mismatch detected
  • Test ran for minimum required duration

No-Ship ❌

Any of these:

  • Primary metric: negative AND statistically significant
  • Guardrail metrics: statistically significant decline
  • Sample ratio mismatch detected (invalidates the test)
  • Test ended early / not enough data

Read the full file on GitHub · 102 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 9d ago First seen · 102 lines · 0 tokens per session scan A 94dede939cb8

Subscribe to this mod's changes

ab-test-analysis is an agent published in the GitHub repository alexmmatos/arthur-mcp (2 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 975 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.