design-experiment

design-experiment is a command for Claude Code from alexclowe/awesome-claude-cowork-plugins. It costs 17 tokens per session (569 once invoked), scanned A, original, MIT.

An experiment-planning assistant for A/B tests, which compare two versions or groups, and other controlled experiments. It estimates how much data is needed and how long a test should run.

In plain words
What is it for?
Use it to define hypotheses and metrics, calculate sample size and statistical power, estimate test duration, and list risks and guardrails.
Why use it?
It helps avoid ending a test too early, missing a meaningful change, or drawing conclusions from weak measurements. It also calls out issues such as seasonal traffic and checking results too often.

Command for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Part of the data-scientist plugin — 2 skills, 4 commands shipped together

Good fit Use it to define hypotheses and metrics, calculate sample size and statistical power, estimate test duration, and list risks and guardrails.

Compare 6 commands from other repositories ↓
Install with agentmods
npx agentmods add commands/alexclowe/awesome-claude-cowork-plugins/design-experiment
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/alexclowe/awesome-claude-cowork-plugins

Made for: Claude Code.

Or install data-scientist, the plugin that ships this one along with the rest of its 2 skills, 4 commands.

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 design-experiment

README.md
[![agentmods](https://agentmods.dev/badge/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment/github.svg)](https://agentmods.dev/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment)
Your own site
<a href="https://agentmods.dev/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment"><img src="https://agentmods.dev/badge/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment/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 design-experiment

Your own site · 80×15
<a href="https://agentmods.dev/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment"><img src="https://agentmods.dev/badge/commands/alexclowe/awesome-claude-cowork-plugins/design-experiment.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 569 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 $0.00017 $0.00569
Opus 5.5 $0.00007 $0.00228
Sonnet 5.5 $0.00003 $0.00114
Haiku 4.5 $0.00002 $0.00057

Measured 23d ago against content hash 2b57c3b2e817, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

design-experiment 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 23d 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.

data-scientist/commands/design-experiment.md · 54 lines

How it starts

The opening of the file, as written. The whole thing — 54 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a data-science assistant helping a data scientist design a rigorous experiment.

The user will describe an experiment goal, a primary metric, current baseline, target effect size, and traffic available. Your job is to:

  1. Restate the experiment — primary metric, hypothesis (H0 / H1), unit of randomization, arms and allocation
  2. Compute sample size — required N per arm given baseline rate, minimum detectable effect, alpha (default 0.05), power (default 0.80)
  3. Recommend duration — given traffic per day, compute test duration; flag day-of-week / seasonality concerns if duration is short
  4. Identify risks and guardrails — secondary metrics, guardrail metrics that must not regress, peeking risk, novelty effect, and any data-quality preconditions

Output format

Structure your response as:

Experiment Plan

  • Goal and hypothesis (H0 / H1)
  • Primary metric, secondary metrics, guardrail metrics
  • Unit of randomization
  • Arms and allocation

Sample Size and Power

  • Baseline rate: X
  • Minimum detectable effect: X (absolute and relative)
  • Alpha: 0.05 | Power: 0.80
  • Required N per arm with the formula or method used (Z-test of proportions, t-test, etc.)

Duration and Schedule

  • Days required at current traffic
  • Recommended start and stop dates accounting for weekly seasonality (full weeks)

Risks and Guardrails

  • Peeking and early-stop risk
  • Novelty / primacy effect concerns
  • Required pre-analysis checks (SRM, A/A test)

Summary / Next steps

Pre-registration checklist and pointer to /analyze-dataset for any baseline data audit.

Important guidelines

  • Use frequentist sample-size formulas (Z-test for proportions, t-test for means) by default; flag when sequential testing or Bayesian methods would be more appropriate
  • Always recommend full-week durations to control for day-of-week seasonality
  • Flag Sample Ratio Mismatch (SRM) as a required check before analyzing — per Kohavi, Tang, and Xu (Trustworthy Online Controlled Experiments)
  • Never recommend stopping early on a positive result without sequential test correction
  • This output is a draft for data-scientist review — the data scientist must confirm assumptions before launching

Read the full file on GitHub · 54 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. 23d ago First seen · 54 lines · 17 tokens per session scan A 2b57c3b2e817

Subscribe to this mod's changes

design-experiment is a command published in the GitHub repository alexclowe/awesome-claude-cowork-plugins (30 stars, last pushed 4d ago), licensed MIT. It adds 17 tokens to every session and 569 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-24.