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Run npx skillmds@latest add ashfordeou/mmpsd-allowables in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Mmpsd Allowables free to use?

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Who published Mmpsd Allowables?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Mmpsd Allowables by ashfordeou — Agent Skill

Name: Mmpsd Allowables
Author: ashfordeOU

Mmpsd Allowables

Use when computing statistically based metallic material design allowables per MMPDS: determine A-basis and B-basis values from coupon test data, run the one-sided normal tolerance k-factor approximation, and validate that derived allowables sit below the sample mean. The skill applies minimum sample counts, confidence/content conventions, and sanity checks on design values, following the statistical approach of MMPDS and its MIL-HDBK-5 heritage. Trigger: allowables, a-basis, b-basis, k-factor, metallic materials, sample statistics, design values, mil-hdbk-5, test specimens.

ashfordeOU Updated Sep 17, 2026

File contents

MMPDS Metallic Allowables (structures/materials/mmpsd-allowables)

Use when the task is statistically based metallic material design allowables: A-basis and B-basis values from coupon test samples, one-sided normal tolerance k-factors, and design-value sanity checks.

Domain quick reference

A-basis: 95% confidence that 99% of the population exceeds the value; B-basis: 95% confidence that 90% exceeds the value.
One-sided normal tolerance k-factor (Owen/Odeh approximation): z_c = 1.6448536269514722 (0.95 confidence); z_p = 2.3263478740408408 for A-basis content or 1.2815515655446004 for B-basis; a = 1 - z_c^2/(2(n-1)); b = z_p^2 - z_c^2/n; k = (z_p + sqrt(z_p^2 - a*b))/a.
Allowable = sample mean - k * sample standard deviation.
Common minimum samples: 10 for A-basis, 6 for B-basis; verify against the current MMPDS edition.
MMPDS is the successor to MIL-HDBK-5 for metallic allowables.

Workflow

Gather the coupon test sample for the material, condition, and property of interest; check the sample count against min_samples.
Compute the k-factor with k_factor_one_sided for the basis.
Compute the allowable with allowable_from_sample.
Sanity-check the result with design_value_sanity: the allowable must be positive and below the sample mean.
Confirm the deterministic checks with the contract test scripts/test_mmpsd.py.

Pitfalls

Using a B-basis k-factor when A-basis is required (A is always lower/more conservative).
Computing k-factors from samples below the minimum count.
Applying the normal tolerance method to skewed or multimodal data without transformation.
Copying design-value tables from MMPDS; derive values from the sample statistics instead.

Behavior contract (gate 3)

The k-factor, sample, and sanity-check logic is exercised by the gate 3 contract test: scripts/test_mmpsd.py against scripts/mmpsd_logic.py (stdlib unittest, offline). Run: python3 scripts/test_mmpsd.py

Compliance

Standards referenced, not reproduced: MMPDS is proprietary (SAE, successor to public-domain MIL-HDBK-5); name + paraphrase
- link only per standards-map.yaml and brief 06; never reproduce design-value tables.
compliance: STANDARDS-REF, gated: false.

---name: mmpsd-allowablesdescription: Use when computing statistically based metallic material design allowables per MMPDS: determine A-basis and B-basis values from coupon test data, run the one-sided normal tolerance k-factor approximation, and validate that derived allowables sit below the sample mean. The skill applies minimum sample counts, confidence/content conventions, and sanity checks on design values, following the statistical approach of MMPDS and its MIL-HDBK-5 heritage. Trigger: allowables, a-basis, b-basis, k-factor, metallic materials, sample statistics, design values, mil-hdbk-5, test specimens.license: Apache-2.0---# MMPDS Metallic Allowables (structures/materials/mmpsd-allowables)Use when the task is statistically based metallic material designallowables: A-basis and B-basis values from coupon test samples,one-sided normal tolerance k-factors, and design-value sanitychecks.## Domain quick reference- A-basis: 95% confidence that 99% of the population exceeds the value; B-basis: 95% confidence that 90% exceeds the value.- One-sided normal tolerance k-factor (Owen/Odeh approximation): z_c = 1.6448536269514722 (0.95 confidence); z_p = 2.3263478740408408 for A-basis content or 1.2815515655446004 for B-basis; a = 1 - z_c^2/(2(n-1)); b = z_p^2 - z_c^2/n; k = (z_p + sqrt(z_p^2 - a*b))/a.- Allowable = sample mean - k * sample standard deviation.- Common minimum samples: 10 for A-basis, 6 for B-basis; verify against the current MMPDS edition.- MMPDS is the successor to MIL-HDBK-5 for metallic allowables.## Workflow1. Gather the coupon test sample for the material, condition, and property of interest; check the sample count against min_samples.2. Compute the k-factor with k_factor_one_sided for the basis.3. Compute the allowable with allowable_from_sample.4. Sanity-check the result with design_value_sanity: the allowable must be positive and below the sample mean.5. Confirm the deterministic checks with the contract test scripts/test_mmpsd.py.## Pitfalls- Using a B-basis k-factor when A-basis is required (A is always lower/more conservative).- Computing k-factors from samples below the minimum count.- Applying the normal tolerance method to skewed or multimodal data without transformation.- Copying design-value tables from MMPDS; derive values from the sample statistics instead.## Behavior contract (gate 3)The k-factor, sample, and sanity-check logic is exercised by thegate 3 contract test: scripts/test_mmpsd.py againstscripts/mmpsd_logic.py (stdlib unittest, offline). Run:python3 scripts/test_mmpsd.py## Compliance- Standards referenced, not reproduced: MMPDS is proprietary (SAE, successor to public-domain MIL-HDBK-5); name + paraphrase + link only per standards-map.yaml and brief 06; never reproduce design-value tables.- compliance: STANDARDS-REF, gated: false.

Frequently asked questions