power-analysis

power-analysis is a skill for Claude Code, Codex from matthewdigiuseppe/MStack. It costs 56 tokens per session (974 once invoked), scanned A, original, MIT.

A statistical planning step that calculates how many observations a study needs and what size of effect it can reliably detect. It uses R simulations and study-design assumptions.

In plain words
What is it for?
Use it to plan sample size, statistical power, and the minimum detectable effect after choosing a research design and before collecting data or registering the study.
Why use it?
It helps avoid running a study that is too small to answer its main question or collecting far more data than necessary.

Skill for Claude CodeCodex

Installs and runs on its own, but its text points at files inside its plugin — anything it tells you to read at a ${CLAUDE_PLUGIN_ROOT} path is only there once the plugin is installed. Installing the plugin gets both.

Part of the mstack plugin — 38 skills, 1 hook shipped together

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.

agentmods
npx agentmods add skills/matthewdigiuseppe/mstack/power-analysis
Any agent
npx skills add matthewdigiuseppe/MStack --skill power-analysis
Clone the repo
git clone --depth 1 https://github.com/matthewdigiuseppe/MStack

Made for: Claude Code, Codex.

Or install mstack, the plugin that ships this one along with the rest of its 38 skills, 1 hook.

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 power-analysis

README.md
[![agentmods](https://agentmods.dev/badge/skills/matthewdigiuseppe/mstack/power-analysis.svg)](https://agentmods.dev/skills/matthewdigiuseppe/mstack/power-analysis)
Your own site
<a href="https://agentmods.dev/skills/matthewdigiuseppe/mstack/power-analysis"><img src="https://agentmods.dev/badge/skills/matthewdigiuseppe/mstack/power-analysis.svg" alt="Measured on agentmods" height="20"></a>
Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 974 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00056 $0.00974
Opus 5 $0.00028 $0.00487
Sonnet 5 $0.00011 $0.00195
Haiku 4.5 $0.00006 $0.00097

Measured 4d ago against content hash a8a68825f005, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

power-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 4d 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.

skills/power-analysis/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/mstack:power-analysis

Stage: design Voice: methodologist

When to invoke

After /mstack:design-research chooses a design. Before fielding. The prereg's "Sample" section pulls its target N from this skill's output.

Procedure

  1. Load. .mstack/hypotheses.md, .mstack/design-research.md, .mstack/lit-map.md (look up effect sizes from comparable studies).

  2. Decide the inputs.

    • Effect-size target. Either:
      • Smallest effect of substantive interest (SESOI), or
      • Median effect from comparable studies in lit-map.md. Be honest: published effects are inflated; aim conservative.
    • α (typically 0.05, two-sided).
    • Power (typically 0.80; for high-stakes preregistered work, 0.90).
    • Design constants — clustering, ICC, attrition rate, blocking.
  3. Write code/00-power.R. Start from the bundled template — copy ${CLAUDE_PLUGIN_ROOT}/skills/power-analysis/assets/00-power-template.Rcode/00-power.R, then adapt the PARAMETERS block and the declared design to the actual study. It:

    • Defaults to DeclareDesign (https://declaredesign.org/r/declaredesign/) — declare the model, inquiry, data strategy, and answer strategy, then diagnose_design() over a grid of N and effect sizes. This is the default because it generalizes across experimental, survey, FE, panel, hierarchical, and conjoint designs, and forces the design assumptions to be made explicit.
    • Use pwr only as a quick analytic sanity check for textbook cases (two-sample t-test, single-level proportion). Use Superpower only for factorial ANOVA designs where DeclareDesign would be overkill. Note the fallback choice and its justification in the script header.
    • For experiments / surveys: report N for power = 0.80 and MDE at the user's planned N.
    • For observational with FE: simulate to find effective N for identification.
    • Saves a sensitivity curve (power vs. effect size; MDE vs. N) to output/figures/power-sensitivity.pdf.

Read the full file on GitHub · 69 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 4d ago First seen · 69 lines · 56 tokens per session scan A a8a68825f005

Subscribe to this mod's changes

power-analysis is a skill published in the GitHub repository matthewdigiuseppe/MStack (14 stars, last pushed 7d ago), licensed MIT. It adds 56 tokens to every session and 974 once invoked, about $0.0003 per session on Opus 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 2026-08-30.

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