A/B Test Analysis

Rigorous A/B test statistical analysis — significance calculations, sample ratio mismatch checks and test design validation.

You say
Install this skill Read the source first Free Written by nimrodfisher · unverified publisher
Context cost
3.8k tokensestimated from the bundle, loaded when it triggers
Bundle
4 files · 15.2 kB1 script among them — read before you run
Licence
free to use
Last change
no release on file
Servers it uses
Noneruns standalone

What it does

Rigorous A/B test statistical analysis. Use when analyzing experiment results, calculating statistical significance, checking for sample ratio mismatch, or validating test design before launch.

Installed, it changes the agent in these ways.

What this skill changes about the agent is not written down here yet. The listing was collected from its source, and the description is in its own SKILL.md.

Expertise

Domain judgement the base model does not have.

ab-testingstatisticsexperimentation

The skill itself

This is the whole product. A skill is instructions the model reads, so there is nothing behind the listing you cannot see first — the front matter loads with every session, and the body below it loads when the skill triggers.

SKILL.md2.9 kB · 35 lines
--- name: ab-test-analysis description: Rigorous A/B test statistical analysis. Use when analyzing experiment results, calculating statistical significance, checking for sample ratio mismatch, or validating test design before launch. ---
6# A/B Test Analysis
7
8# When to use
9- An experiment has finished and the team needs a ship / no-ship recommendation
10- Results look directionally positive but the team is unsure if they're statistically significant
11- A test has been running for weeks without a clear winner and someone needs to decide whether to continue
12- A new experiment needs sample-size planning before launch
13- Results are disputed and need a rigorous, documented analysis
14
15# Process
161. **Confirm test design** — verify the hypothesis, the control and treatment definitions, the randomisation unit (user/session/device), the primary metric, any guardrail metrics, and the target split ratio.
172. **Check for sample ratio mismatch (SRM)** — run a chi-square test on the actual vs. expected split. If SRM is detected, stop and investigate the randomisation pipeline before interpreting results. Use scripts/ab_test_analyzer.py --check-srm.
183. **Calculate per-variant metrics** — compute the rate (or mean) and 95% confidence interval for the primary metric in each variant. Document absolute and relative difference.
194. **Run the significance test** — execute a two-proportion z-test (for rates) or Welch's t-test (for means). Record z-score, p-value, and 95% CI for the effect. Use references/statistical_tests_reference.md if unsure which test applies.
205. **Check guardrail metrics** — run the same significance test for each guardrail metric. A significant degradation on any guardrail is a blocker regardless of primary metric results.
216. **Produce the recommendation** — synthesise SRM result, power, significance, and guardrail checks into a clear ship / no-ship / extend decision. Quantify the expected business impact if shipped. Record in assets/ab_test_report_template.md.
22
23# Inputs the skill needs
24- Test plan or hypothesis document (variant definitions, randomisation unit, primary metric)
25- Data with at minimum: user_id, variant assignment, primary metric outcome
26- Optional: guardrail metric values per user, daily aggregate data for temporal validity checks
27- Target split ratio (e.g., 50/50)
28- Minimum detectable effect or business threshold for "worth shipping"
29
30# Output
31- scripts/ab_test_analyzer.py — runs SRM check, significance test, power analysis, and guardrail checks from a CSV or summary stats input
32- references/statistical_tests_reference.md — which test to use and when
33- references/ab_test_design_guide.md — SRM causes, power planning, peeking and multiple testing
34- assets/ab_test_report_template.md — structured report: design, results, checks, recommendation, expected impact
35
In the file
SKILL.md398 words
Files4
Licence
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈60
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
3,740
on trigger
The instruction body and 3 supporting files, read only when the skill fires.
1.9%
of a 200k window
Ten skills this size would take about 19% of the window before you open a file.
050k100k150k200k context window

3.8k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

Adoption
Installsnone yet
Ratingno reviews yet

The procedure it runs

The procedure has not been published here. It is in the skill’s own SKILL.md, which its author has not sent to the marketplace yet.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

It writes no files and reaches no network. All it changes is how the model reasons and writes.

What it asks for
Writes filesno
Network accessno

Read from the allowed-tools line of this skill’s own SKILL.md. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

4 files, 15.2 kB on disk. Mostly text — the instructions the model reads — with 1 script in it that your client would run only if the instructions tell it to.

  • SKILL.md2.9 kB
  • assets/ab_test_report_template.md2.0 kB
  • references/ab_test_design_guide.md3.3 kB
  • scripts/ab_test_analyzer.py7.0 kB
What is not in it

A skill installs nothing and depends on nothing: it is a folder your client reads. This one carries 1 script beside the text, so the bundle is 4 files you can review in full before installing.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# A/B Test Analysis · 3.8k tokens when loaded npx mcprush@latest skill add nimrodfisher/a-b-test-analysis

Writes to .claude/skills/a-b-test-analysis/ in the current project. Add --global to put it in your home directory instead, for every project.

Which clients pick it up on their own

A skill is a folder of text. A client with a skills folder reads it without being told; everywhere else the same text works, it is just handed to the model rather than found.

Claude Code.claude/skills/
Claude Desktop
ChatGPT
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok.grok/skills/
Zed.agents/skills/
Windsurf.windsurf/skills/
Agent SDK.claude/skills/
HTTP / API
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencenimrodfisher/a-b-test-analysis

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v
  • No earlier releases have been published to the marketplace.
Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

no reviews yet · no installs yet

Nobody has reviewed this skill yet. The rating is the mean of the reviews written here, so there is none until somebody writes the first.

Who can post

Only accounts that have had the skill installed for fourteen days, so a review is written after living with it rather than after reading it. Publishers may reply once.

Who wrote it

NI
nimrodfisher

Publishes on mcprush.

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