Paid Ads Experiment Log — hypothesis-first change journal + directional lift

Paid changes rarely get measured — the budget moves, the creative swaps, and three weeks later nobody can say whether it helped. This skill logs each change with its hypothesis at the moment you make it, then reads the before/after once the window closes — honestly, as a directional read on a live account, never a controlled experiment.

Adapted from github.com/stan-default/liam's compute_lift + liam-experiments (MIT), accessed 2026-07-14, via /steal — see .claude/discovery/0726-liam-steal-analysis.md. Concept port; no code reused.

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Doctrine inherited

• quantitative-evidence-floors.md — lift is directional and floored. No "it worked" below the volume floor; state the counts, name the lag.
• linkedin-ads-spend.md — read tools only. This skill never calls a write tool.
• financial-data.md + pii-redaction.md + storage-policy.md — ads data is client-confidential. The journal lives in the client folder; never commit it or raw exports to git; never fabricate a figure the MCP didn't return.

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The honesty rule — voice-locked

A before/after on a live account is NOT a controlled experiment. No holdout, no randomization — just the same account before and after, with everything else in the market also moving. If two changes overlapped, or a named confound could own the delta, the answer is inconclusive, not "it worked." A logged "we think this helped, here's the confound that would flip it" beats a confident fabrication every time.

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The two moves

1. Log the change — at the change, not after

One appended JSONL line per material change, written when you make it (the hypothesis is the point — a change logged without one can only be rationalized later, not judged):

{"date":"2026-07-14","account":"<id>","scope":"campaign|ad|group","touched":["<name>"],"change_type":"budget|creative|audience|bid|schedule|offer|structure","from":"<before>","to":"<after>","hypothesis":"<what you expect and why>","expect_metric":"CPL","expect_direction":"down","baseline_window":"2026-06-30..2026-07-13","baseline":{"spend":0,"impressions":0,"clicks":0,"ctr":0,"conversions":0,"cpl":0,"conv_rate":0}}

Baseline = the pre-change metrics over a window the same length as the after-window you'll measure against. Store at {client}/paid/execution/paid-change-journal.jsonl (append-only, client-confidential).

2. Read the lift — once past the attribution window

1. Pull the after-window (same length as baseline) via the MCP read tools (get_campaign_performance, get_daily_trends, compare_performance). Never a write tool.
2. Compute before → after on the hypothesis metric + the guardrail metrics (don't let CPL drop while conversions crater).
3. Floor it. Below the volume floor (quantitative-evidence-floors.md — <3 conversions, <~100 clicks, before a full window) → "too early, re-read at N", not a verdict.
4. Name the confounds. Seasonality, other concurrent changes, audience fatigue, attribution lag, denominator swings. If one could own the delta, the read is inconclusive.
5. Verdict language: directionally validated / directionally invalidated / inconclusive (confound: X) — never "proven."

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Anti-patterns

• ❌ Logging a change with no hypothesis — then you're rationalizing, not measuring.
• ❌ Calling a before/after a "test" or the result "proven."
• ❌ Crowning lift below the volume floor (a 30% CPL move on 5 conversions is noise).
• ❌ Ignoring a concurrent change that could own the delta.
• ❌ Committing the journal or a raw export to git — client folder only.

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Integration with other skills

• Feeds /paid-ads-audit — the journal is the "what we changed and what happened" context the audit reads.
• Feeds /paid-campaign-strategy — validated changes inform the refresh.
• Sibling to /ab-testing — that's a controlled test (holdout, randomization); this is observational before/after. Reach for /ab-testing when you can run a real split; reach for this when you can't and just need an honest read on a live change.

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Final ship gate

Run /premortem --output before ship. See /premortem skill for the 5 execution domains + output template.

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