---
name: project-step1379-cohen-d-both-2026-08-23
description: "STEP 1379 STEP 1376 v0.2 Cohen's d threshold BOTH 経路 拡張 — cohenDMin 引数追加、activate 4/8 → 5/8、backward compat 維持"
metadata: 
  node_type: memory
  type: project
  originSessionId: 1f71dc26-eff6-41db-8142-70648b0a0ec2
  modified: 2026-08-22T21:57:36.024Z
---

# STEP 1379 — Cohen's d threshold BOTH 経路 (STEP 1376 v0.2)

Date: 2026-08-23
Status: 実装 + test 39/39 + MCP smoke verify 完了
契機: STEP 1376 v0.1 honest scope §3 の v0.2 拡張 candidate

## 実装

src/mcp/d8-verdict-mapping.ts:
- SamplePairInput に cohenDMin?: number | null optional 追加
- SamplePairPayload に cohenDMinUsed: number | null 追加
- mapSamplePairToD8 S5 branch 3 分岐: S5 (v0.1) / S5b (BOTH) / S5c (TRUE_above)
- d8SamplePairSpecTable = 8 rules (S1-S6 + S5b + S5c)
- SAMPLE_PAIR_HONEST_SCOPE update = 5/8 activate marker

src/mcp/rei-mcp-server.ts:
- d8_verdict_from_sample_pair tool description v0.2 化 + inputSchema cohenDMin field 追加 + case handler pass-through
- Banner 変更なし (tool count 41 不変、v2.8.4 のまま、STEP 1378 auto-count 継承)

## 決定表 v0.2 (8 rules)

| # | Condition | Verdict | Reason |
|---|---|---|---|
| S1 | sample size < 2 | NEITHER | insufficient_sample |
| S2 | alpha invalid | NEITHER | alpha_not_set |
| S3 | var=0 mean=0 | FALSE | zero_variance_zero_diff |
| S4 | var=0 mean≠0 | INFINITY | deterministic_difference |
| S5 | p<α cohenDMin null (v0.1 mode) | TRUE | significant_effect |
| **S5b** | p<α \|d\|<cohenDMin | **BOTH** | significant_but_tiny_effect |
| **S5c** | p<α \|d\|≥cohenDMin | **TRUE** | significant_effect_above_threshold |
| S6 | p≥α | FALSE | no_significant_effect |

v0.2 activate 5/8 (TRUE/FALSE/NEITHER/INFINITY/BOTH)、v0.1 4/8 + BOTH 追加。
ZERO/FLOWING/SELF 予約。

## Verify

- test/step1379: 39/39 PASS
- test/step1376 regression: 64/64 PASS (v0.2 spec 期待値 update 後)
- MCP smoke: cohenDMin=0.2 で Cohen d=-3.30 → S5c → TRUE significant_effect_above_threshold ✓

## Cohen 1988 conventional

\|d\| < 0.2 = small / 0.2 ≤ \|d\| < 0.5 = medium / \|d\| ≥ 0.5 = large / 0.8+ = very large

## Backward compat

- cohenDMin 未設定/null/invalid → v0.1 挙動維持 (breaking change ゼロ)
- MCP tool 数 41 不変、banner v2.8.4 のまま (STEP 1378 auto-count)

## Site + 関連

- URL: https://rei-aios.pages.dev/tools/step-1379-cohen-d-both/
- STEP 1376/1378 直接依存、STEP 1350/1371/1377 相補 domain、STEP 1358/1359 参照
- Cohen 1988 conventional threshold origin