A/B Test Sample Size Calculator MCP Server

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answering

A/B Test Sample Size Calculator MCP is answering right now. Last checked 15 min ago. It exposes 5 tools. Last commit 3 Nov 2026.

Exact A/B test sample size, duration, z-test, chi-square, Fisher-Freeman-Halton and peeking risk.

Uptime history 6 days of history

6 days agonow

100.0%

Uptime 24h

91 of 91 checks

Tools

read from the server

217 ms

Response time

average over 24h

Stars

last commit 3 Nov 2026

Nothing serious here today

Today is the operative word: we check A/B Test Sample Size Calculator MCP every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 15 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add ab-test-sample-size-calculator-mcp --transport http https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp

Settings → Connectors → Add custom connector, then paste this address

https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp

~/.codex/config.toml

[mcp_servers.ab-test-sample-size-calculator-mcp]
url = "https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "ab-test-sample-size-calculator-mcp": {
      "url": "https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

.vscode/mcp.json

{
  "servers": {
    "ab-test-sample-size-calculator-mcp": {
      "type": "http",
      "url": "https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

Available tools 5

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

calculate

calculate_sample_size

Exact sample size per variant for an A/B test on a conversion rate (two independent proportions): baseline rate, minimum detectable effect (relative or absolute), alpha, power, one or two-sided, several variants with optional Bonferroni, and unequal allocation. Uses the pooled/unpooled normal formula (same as R power.prop.test) and also reports the figure Evan Miller's calculator gives, so the two can be reconciled.

estimate

estimate_test_duration

How many days an A/B test must run: from a known sample size per variant, or from baseline rate and MDE (computed as in calculate_sample_size), plus daily visitors and the share of traffic in the test. Returns exact days and the recommended whole weeks (to cover weekday effects).

fisher

fisher_exact_test

Exact p-value for a contingency table of counts. 2x2: Fisher exact test (two-sided, greater or less, as R fisher.test). Larger r x c tables (for example 3 variants x converted/not, or 4 x 4 survey tables): Fisher-Freeman-Halton exact test by a network algorithm. Also returns Pearson chi-square and how many cells have expected counts below 5, so you can see when the chi-square approximation is unsafe.

peeking

check_peeking_risk

What peeking does to an A/B test: the real false positive rate if you check a fixed-horizon test K times and stop at the first p < alpha (for example about 14% at 5 looks with alpha 0.05), and the Pocock and O'Brien-Fleming group sequential boundaries (z and nominal p per look) that keep the overall rate at alpha, for up to 10 equally spaced looks.

test

test_ab_significance

Is an A/B test result statistically significant? From visitors and conversions per group: two-proportion z-test (pooled), one or two-sided p-value, Wald confidence interval for the difference, relative lift, Pearson chi-square with and without Yates correction (R prop.test), Fisher exact p for the same 2x2 table, and a sample ratio mismatch (SRM) check against the planned split.

Endpoints

URL	Transport	State	Latency	Checked
https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp	streamable-http	answering	271 ms	15 min ago

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A/B Test Sample Size Calculator MCP — questions

Answers built from our own checks of this server.

What can A/B Test Sample Size Calculator MCP do?

It exposes 5 tools, read directly from the server on our last check. Among them: calculate_sample_size, check_peeking_risk, estimate_test_duration, fisher_exact_test, test_ab_significance. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is A/B Test Sample Size Calculator MCP working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 217 ms. The bar chart above shows every period we have measured.

How do I connect A/B Test Sample Size Calculator MCP?

Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does A/B Test Sample Size Calculator MCP need an API key?

No. A/B Test Sample Size Calculator MCP completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 5 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is A/B Test Sample Size Calculator MCP?

It answers our handshake in 217 ms on average, which is faster than 65% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.

Is A/B Test Sample Size Calculator MCP open source?

The code is open source: it is published under the MIT licence, written in TypeScript and 0 stars on GitHub. The licence covers the code in the repository, not the hosted service at ab-test-sample-size-calculator-mcp.lipmichal.workers.dev, which runs on its operator's own terms.