Measuring Product-Market Fit

Scope

Covers

• Measuring PMF using a triangulated signal set (survey + behavior + customer evidence)
• Running and interpreting the Sean Ellis “Very Disappointed” survey (overall + by segment)
• Reading retention curves / cohort retention as PMF evidence (and knowing when they mislead)
• Using reference-customer / advocacy signals as an additional PMF proxy
• Detecting PMF drift (market shifts, rising expectations, competitive resets) and setting a re-measurement cadence
• Special handling for marketplaces (measure PMF per side; focus on the “hard side” first)

When to use

• “Do we have PMF? For which segment?”
• “Run a Sean Ellis PMF survey and tell me what it means.”
• “Build a PMF scorecard with retention + survey + references.”
• “Our market shifted—did we lose PMF?”
• “We want a go/no-go signal for scaling growth spend or launching publicly.”

When NOT to use

• You haven’t defined the problem/ICP yet (use problem-definition).
• You only need a survey instrument, not a full PMF measurement system (use designing-surveys).
• You’re deciding whether/how to pivot (use startup-pivoting) rather than measuring PMF signals.
• You need a product vision/strategy doc as the primary output (use defining-product-vision / ai-product-strategy).

Inputs

Minimum required

• Product + category + current stage (pre-PMF / early PMF / growth / mature)
• Business model: B2B / B2C / marketplace (and, for marketplaces, which side you’re focusing on)
• Your current best guess at the target segment/ICP (and any meaningful segments)
• Definition of active user and the core value moment (the action that indicates value received)
• What data you can access: survey channels, product analytics, retention cohorts, revenue, qualitative feedback, reference customers/testimonials
• Time horizon and constraints (deadline, privacy/PII constraints, internal-only vs shareable)

Missing-info strategy

• Ask up to 5 questions from references/INTAKE.md, then proceed.
• If key inputs are missing, proceed with explicit assumptions and label confidence.
• Do not request secrets. If data includes PII, ask for redacted excerpts or aggregated fields.

Outputs (deliverables)

Produce a PMF Measurement Pack (Markdown in-chat; or as files if requested) containing:

1. Context snapshot (product, stage, decision, timebox, segments, constraints)
2. PMF measurement model (core value moment, active user definition, signal set, thresholds as heuristics)
3. Sean Ellis survey plan + results (sample definition, questions, response counts, “very disappointed” % overall + by segment, top benefits)
4. Behavioral evidence (retention/cohort summary + engagement frequency; instrumentation gaps + how they affect confidence)
5. Reference-customer / advocacy evidence (who is willing to vouch; quotes; counts vs heuristic targets)
6. PMF Scorecard (signals, targets, current state, confidence, evidence links/notes)
7. Diagnosis + action plan (PMF status by segment; top drivers; prioritized next actions/experiments)
8. Risks / Open questions / Next steps (always included)

Templates and checklists:

• references/TEMPLATES.md
• references/CHECKLISTS.md
• references/RUBRIC.md

Workflow (7 steps)

1) Intake + decision framing

• Inputs: User context; references/INTAKE.md.
• Actions: Confirm the decision (scale spend, launch, refocus ICP, pricing), the timebox, and the audience. Define “what will we do differently based on this?”
• Outputs: Context snapshot + measurement constraints.
• Checks: A stakeholder can answer: “What decision will this change by ?”

2) Define the PMF measurement model (and segments)

• Inputs: Product + segment hypotheses; data availability.
• Actions: Define:
  • The core value moment and active user definition
  • The segment(s) to evaluate (ICP + meaningful slices)
  • The signal set (survey + behavior + customer evidence) and what “good” looks like (as heuristics)
• Outputs: PMF measurement model + segment plan.
• Checks: Each signal has (a) a metric definition, (b) a data source, and (c) a limitation note.

3) Run the Sean Ellis PMF survey (must-have test)

• Inputs: Target population list (active users); distribution channel; references/TEMPLATES.md (PMF block).
• Actions: Draft and run:
  • “How would you feel if you could no longer use ?” (Very / Somewhat / Not disappointed)
  • Follow-up: “What is the primary benefit you receive?” (text)
  • Segment respondents (persona/ICP, use case, tenure) to find the “must-have” cohort
• Outputs: Survey plan + results table (overall + by segment) + top benefit themes.
• Checks: Sample definition is explicit; results include counts (n), not only percentages; major bias risks are listed.

4) Analyze behavioral evidence (retention + engagement)

• Inputs: Product usage data or best-available proxy; activation definition.
• Actions: Build a minimal behavioral picture:
  • Cohort retention (or repeat usage/purchase) by segment and tenure
  • Retention curve shape (improving/flat/decaying) and interpretation
  • Engagement frequency vs the product’s natural cadence (daily/weekly/monthly)
• Outputs: Retention/engagement summary + confidence notes + instrumentation gaps.
• Checks: Retention is measured from a clear cohort start; analysis separates activation from retention.

5) Collect reference-customer / advocacy evidence

• Inputs: Customer list; CS/sales notes; reviews; testimonials.
• Actions: Identify users willing to vouch publicly/privately:
  • B2B heuristic target: 6–8 reference customers
  • B2C heuristic target: 15–25 strong references/advocates
  • Capture the “why” (benefit) and the segment they represent
• Outputs: Reference evidence log + gaps by segment.
• Checks: References map to the intended ICP/segment; evidence is current (not from a different market era).

6) Synthesize into a PMF scorecard + diagnosis (by segment)

• Inputs: Survey + behavior + reference evidence.
• Actions: Triangulate signals to answer:
  • Do we have PMF for any segment? Which one is strongest?
  • What are the top drivers of “must-have” value?
  • What’s blocking PMF for adjacent segments?
  • Are we at risk of PMF drift (market shift, expectations rising)?
• Outputs: PMF Scorecard + diagnosis narrative + confidence rating.
• Checks: Diagnosis is segment-specific and evidence-backed; “unknowns” are explicit.

7) Quality gate + action plan + cadence

• Inputs: Draft pack; references/CHECKLISTS.md and references/RUBRIC.md.
• Actions: Run the checklist + score with rubric. Produce:
  • Prioritized next actions/experiments (what to change, how to measure impact)
  • A PMF re-measurement cadence + drift triggers
  • Risks / Open questions / Next steps
• Outputs: Final PMF Measurement Pack.
• Checks: Actions are concrete enough to execute next sprint/quarter; measurement plan includes owners and dates (if known).

Quality gate (required)

• Use references/CHECKLISTS.md and references/RUBRIC.md.
• Always include: Risks, Open questions, Next steps.

Examples

Example 1 (B2B SaaS, early growth):
“Use measuring-product-market-fit. Product: AI meeting notes for account executives. Segments: mid-market sales teams vs SMB founders. Data: 90-day cohorts + in-app survey. Decision: whether to scale paid acquisition next quarter. Output: a PMF Measurement Pack.”

Example 2 (Marketplace, supply-first):
“We’re building a caregiver marketplace. We have early demand, but supply is thin. Measure PMF for the supply side first using a PMF survey + retention proxies. Output a scorecard and a plan to strengthen the core value exchange.”

Boundary example (insufficient inputs):
“Do we have PMF?”
Response: ask up to 5 intake questions (segment, active user definition, data sources, survey channel, decision), then produce a minimal PMF Measurement Pack with explicit assumptions and confidence limits.