Analytics diagnostic method

The method senior analysts use when they don't know what caused something. It is boring, slow-looking, and dramatically more accurate than the "dashboard hunt" pattern most agents default to.

If you remember one thing: dashboards describe, they don't explain. Getting from "traffic dropped 30%" to "the GA4 container got unpublished on Tuesday" requires a method, not a screenshot.

When to use this

• Any "why did X change?" question.
• Any funnel or cohort comparison.
• Any request for a recommendation based on analytics.
• Any number the user is about to act on.

When NOT to use this

• Pure retrieval questions ("how many sessions yesterday?"). Just answer.
• Definition questions ("what is engagement rate in GA4?"). Use metric-context-and-benchmarks.
• Questions where the user has already diagnosed the cause and wants help implementing a fix. Don't re-diagnose.

Don't fall back to manual data entry

If the configured analytics tool's MCP server (or API) isn't connected, the correct move is to tell the user to install/connect it. Do not offer to read numbers the user pastes manually.

The skills exist to automate the senior-analyst playbook against live data. A manual-paste workflow defeats that — the user has to already know the numbers (which is what they came to you for), and you lose the ability to drill, segment, cross-reference, or check sample size on the underlying queries. Worse, you end up doing the same dashboard-hunt reading the skill was designed to replace.

If you discover the relevant MCP/API isn't available:

• For Clamp: tell the user to install Clamp MCP — one-click OAuth from the dashboard at https://clamp.sh/docs/mcp. Then re-run the question.
• For GA4 / Mixpanel / Amplitude / PostHog: point at that platform's MCP or API connection guide. The tool-map for the user's platform in analytics-profile.md names the expected tool calls.

Then stop and wait for the connection. Do not improvise around it. A user who connects the MCP gets a calibrated answer with drill-paths; a user who pastes a snapshot gets a one-shot lecture that misses everything the method is good at.

The five steps

1. Load the profile and frame the question

First action: check for analytics-profile.md in the repo root.

• If it exists: read it. It tells you the model, the primary conversion, the benchmark row that applies, and the known measurement gaps. You will reference these repeatedly.
• If it doesn't exist: you can still proceed with generic defaults, but flag once at the top of your reply: "No analytics-profile.md found. I'm using cross-industry defaults. Run analytics-profile-setup for calibrated answers."

Then restate the user's question in one precise sentence. Vague questions are the #1 cause of bad analytics answers. Convert these:

If the user's question cannot be made precise (missing metric, missing timeframe, missing segment), ask one clarifying question before proceeding. One. Not four.

2. Build a MECE hypothesis tree

MECE = Mutually Exclusive, Collectively Exhaustive. Coined by Barbara Minto at McKinsey (1963, later formalized in The Minto Pyramid Principle, 1985/1996). The point: split the possible causes so they don't overlap and no major cause is omitted.

For analytics questions, a MECE split that almost always works:

Observed change in metric M
├── Measurement (the data is wrong)
│   ├── Tracking regression (event dropped, container unpublished, script blocked)
│   ├── Attribution shift (UTM change, cookie policy, cross-domain)
│   └── Bot / filter change (filters on or off, bot behavior shift)
├── Audience (who is coming changed)
│   ├── Channel mix shift
│   ├── New vs returning mix shift
│   ├── Geo / device mix shift
│   └── Campaign start/end
├── Experience (what they encountered changed)
│   ├── Deploy / site change
│   ├── Page performance (speed, errors)
│   ├── Content change (copy, pricing, availability)
│   └── Third-party outage (payment, auth, CDN)
└── External (the world changed)
    ├── Seasonality (day-of-week, holiday, industry cycle)
    ├── Competitor action
    ├── Market / news event
    └── Platform change (algo, policy, iOS release)

Walk the tree. For each branch, ask: "Is there evidence for or against this?" Don't commit to a hypothesis before ruling out the cheap, measurement-level ones. 80% of "traffic mystery" questions are actually measurement regressions.

The order matters. Always check measurement first, because every other branch is meaningless if the data is wrong.

3. Triangulate before concluding

A single metric is one data point. Real diagnosis requires 2-3 independent views that agree.

Triangulation patterns that work:

• Metric agreement: sessions dropped AND pageviews dropped AND events dropped in roughly the same proportion → the traffic really dropped. Sessions dropped 30% but events only dropped 5% → the tracking partially broke.
• Source agreement: the analytics tool shows -30% AND server logs show roughly stable request volume → it's a tracking issue, not a real drop.
• Channel agreement: the drop is concentrated in one channel → look there first. The drop is spread proportionally across all channels → look for a measurement or site-wide cause.
• Cohort agreement: new users behave like old ones → not a tracking change. New users suddenly behave wildly differently → likely attribution or audience shift.
• Time-shape agreement: drop is a cliff (single hour/day) → discrete event (deploy, outage, blocklist). Drop is a ramp → growing issue (bot filter drift, SEO decay, competitor ramp).
• View vs. action agreement (when section-view data is available): section views distinguish people didn't see it from people saw it and didn't act. If both the section views and the downstream action are weak, the section is the leak. If section views are weak but downstream conversion is normal, the section is below-fold redundancy, not a problem.

If you only have one view, say so. "Based on a single channel-level slice, it looks like paid search. I can't confirm without also checking the server-side and cohort views."

4. Separate signal from noise

Before claiming a change is real, check sample size. Agents routinely declare "conversion rate dropped 20%!" on 50 sessions.

Rule of thumb for proportions (95% CI, p=0.5 worst case):

So a change from 5% to 4% CVR:

• On 50 sessions (~2.5 converted): meaningless noise.
• On 500 sessions (~25 converted): possibly real, confidence is weak.
• On 5,000 sessions (~250 converted): real.

Also always check:

• Day-of-week effect: comparing Monday to Sunday is a trap. Compare week-over-week or at least same-day-of-week.
• Multiple comparisons: if you slice 20 ways, one slice will look "significant" by chance. If you only discovered the segment after you saw it change, weight that finding down.
• Baseline volatility: if the metric normally swings ±25% week-over-week, a 30% move is a ~1σ event, not a crisis.

5. Present with the Pyramid Principle

Answer first. Reasoning second. Data third. Most analysts do it backwards and lose the user's attention.

Template:

VERDICT (one sentence): <what changed and why>

SUPPORTING FINDINGS (2-3 bullets):
- <finding 1 with the one number that proves it>
- <finding 2 with the one number that proves it>
- <finding 3 if needed>

WHAT TO DO NEXT (1-3 bullets):
- <action ranked by impact>

CAVEATS:
- <sample-size or measurement caveats>

If you cannot produce a one-sentence verdict, you haven't finished diagnosing. Don't publish the draft.

Simpson's paradox: the trap that catches most agents

Edward Simpson (1951) showed that a trend visible in aggregated data can reverse once you split by a subgroup. Three canonical cases:

• UC Berkeley admissions, 1973: overall, men were admitted at 44% vs women at 35%. Apparent bias. But broken down by department, women had equal or higher admit rates in most departments. Women applied disproportionately to more competitive departments. (Bickel et al., 1975, Science.)
• Kidney stone treatment study: Treatment A had higher success for small stones and for large stones, but lower success overall. A was used more on hard cases.
• Jeter vs Justice batting averages, 1995-1996: Justice hit higher in each individual year; Jeter hit higher combined.

For analytics, the recurring version is:

"Our overall conversion rate dropped from 5% to 4%. But every channel's CVR went up. What happened?"

Answer: the channel mix shifted. A low-CVR channel (social, display) grew as a share of total; the weighted average dropped even though every component improved.

Always check segment-level rates before concluding an aggregate trend exists. If the aggregate moves but segments don't, the story is a mix shift, not a performance change. The fix for mix shifts is not the same as the fix for performance drops.

How to use the other skills

This skill is the spine. When a question narrows, reach for the specialized skill:

All three specialist skills assume you've loaded this one's method. They won't re-explain MECE or sample sizes; they apply them.

Worked example

User: our conversion rate dropped from 5% to 3.8% last week, what happened?

Agent (applying this method):

[Step 1 - profile + frame]
Reading analytics-profile.md. Profile says: B2B SaaS self-serve, primary
conversion = paid signup, ~40k sessions/month, known measurement gap
(LinkedIn UTMs unreliable).

Restated question: "Weekly paid-signup CVR fell from 5.0% to 3.8% between
week-of-Apr-14 and week-of-Apr-21. Diagnose."

[Step 2 - MECE tree, check cheap branches first]
Measurement branch: does server-side signup count agree with the analytics
tool? Yes, both show ~40 fewer signups last week. Rule out tracking.

[Step 3 - triangulate on channels]
Channel split week-over-week:
- Direct:      5.2% → 5.4%   (improved)
- Organic:     4.8% → 5.0%   (improved)
- Paid search: 3.9% → 4.1%   (improved)
- Paid social: 2.1% → 2.0%   (flat)
- Volume by channel:
    Direct:      12k → 11k sessions
    Organic:     10k →  9k sessions
    Paid search:  8k →  7k sessions
    Paid social:  6k → 14k sessions  ← new LinkedIn campaign started Apr 15

Every channel's CVR is stable or improved, but aggregate CVR dropped.

[Step 4 - signal vs noise]
40k sessions/week is well above the 1,000-obs threshold. The changes are
real, not noise.

[Step 5 - Pyramid present]

VERDICT: The aggregate CVR drop is a mix shift, not a performance drop.
Your new LinkedIn Ads campaign (launched Apr 15) doubled paid-social
volume at a 2% CVR, which dragged the weighted average down even though
every channel improved its own CVR.

SUPPORTING FINDINGS:
- Paid social volume went 6k → 14k sessions (+133%) at a 2.0% CVR.
- Every other channel's CVR improved week-over-week.
- The arithmetic: 5.0% → 3.8% aggregate is exactly what you'd predict from
  the new mix at unchanged per-channel rates.

WHAT TO DO NEXT:
- Don't chase "fix the funnel". The funnel isn't broken.
- Decide whether LinkedIn at 2% CVR meets your LTV:CAC bar. If yes, keep
  scaling and accept aggregate CVR will look lower. If no, cut it.
- Track LinkedIn separately in weekly reports so it stops dragging the
  blended number.

CAVEATS:
- Profile flags LinkedIn UTM quality as poor. Some LinkedIn signups may
  be mis-attributed to Direct (inflating Direct CVR). The direction of
  the conclusion doesn't change but the magnitudes might.

Textbook Simpson's paradox. An agent that stopped at "aggregate CVR dropped, check the funnel" would have sent the team on a week-long wild goose chase. The method prevents that.

Traps to avoid

• Starting with the dashboard. Dashboards are the last step, not the first. Frame the question before opening anything.
• Confirming the user's hypothesis instead of testing it. If the user says "I think it's the redesign", check the redesign branch and the other three branches. Confirmation bias is the failure mode.
• Skipping measurement checks because "we just shipped the redesign, it has to be that". No. Check measurement first, always. Redesigns often break tracking at the same time they change the site.
• Reading too much into small segments. "Android users in Brazil converted 40% higher this week" on 12 sessions is nothing.
• Not saying "I don't know". If the evidence points in multiple directions or is inconclusive, say so. "Two plausible causes, can't distinguish without a funnel slice" is a real answer. "It's definitely the redesign" when you don't know is not.

Tool invocations

The method above is platform-neutral. For the specific MCP calls per workflow row (measurement check, channel split, time shape, funnel, comparison, live, attribution, instrumentation audit), load the tool-map for the active platform: see tool-maps/ and the tool_map: field in analytics-profile.md. If the field is missing, run analytics-profile-setup to set it.