# Screening Then Decomposition

> Two-phase sensitivity — Morris quick screening to eliminate unimportant factors, then Sobol precise decomposition on survivors. Efficient allocation of analytical effort.

- Skill: `yogsoth-ai/screening-then-decomposition` (Agent Skill)
- Install (CLI): `npx skillmds@latest add yogsoth-ai/screening-then-decomposition`
- Raw SKILL.md: https://api.skillmd.com/api/skills/yogsoth-ai/screening-then-decomposition/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: yogsoth-ai (https://skillmd.com/u/yogsoth-ai)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/yogsoth-ai/screening-then-decomposition

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# Screening Then Decomposition

Two-phase approach: quick screening followed by precise decomposition.

## Operations

morris-screening → sobol-decomposition → interaction-detection

## Available SOPs

**Subagent:** morris-screening, sobol-decomposition, interaction-detection
**Import:** paper-search

## Execution Guidance

Phase 1 (Morris): Screen all parameters, eliminate those with low mu* and low sigma. These are unimportant and can be safely fixed at nominal values.

Phase 2 (Sobol): For surviving parameters, compute precise variance decomposition. First-order indices (Si) measure direct effects, total-order indices (STi) measure direct + all interactions.

Phase 3: Detect significant interaction pairs (STi - Si > threshold). Characterize interaction types and implications.

## Minimum Yield

```
<HARD-GATE>
- Parameters screened: >= 5
- Parameters eliminated (low mu*): >= 1
- Sobol indices computed: >= 3 parameters
- Interaction pairs identified: >= 1
</HARD-GATE>
```

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## Available SOPs

Optional, no fixed order; the final leaf is always a sop.

| SOP | When to use |
| --- | --- |
| deep-insight-paper-search | AI-powered paper summary and search. Import of literature-engine/literature-search skill. AI summary level — cite as "AI-extracted" not "paper states". |
| interaction-detection | Detect and characterize significant parameter interactions from Sobol decomposition results. |
| morris-screening | Morris method screening — compute elementary effects to quickly identify important vs unimportant parameters. |
| sobol-decomposition | Sobol variance decomposition — compute first-order and total-order sensitivity indices for precise variance attribution. |

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