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Growth analytics

Skill samuelcastro/startup-skills/growth-analytics

Agent Skills for AI-native startup founders — a founder-playbook hub + 12 per-function skills. Adapted from Linas Beliūnas's One-Person Unicorn + Anthropic's Founder's Playbook.

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Guide founders through metrics frameworks, experimentation, and data-driven growth. Use when a founder says "help me set up my metrics framework", "what should my north star metric be?", "design an A/B test", "help me analyze retention/churn", "build me a dashboard to track growth", "how do I do cohort analysis?", "what metrics should I track?", "pirate metrics", "AARRR funnel", or needs to make sense of their growth data.

SKILL.md

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Growth & Analytics

Guide founders from defining their first metrics (pre-launch) through sophisticated retention analysis and experimentation (post-launch).

Workflow

1. Diagnose Current State

Ask: "Where are you in your analytics journey?"

StateSignalsNext Step
Pre-launchNo users yet, needs to define what to track→ Step 2: Metrics Framework
Early tractionHas users, unclear what metrics matter→ Step 2: Metrics Framework
Tracking basicsHas metrics, needs North Star focus→ Step 2: North Star Selection
Ready to experimentSolid metrics, wants to run tests→ Step 3: A/B Testing
Retention concernsUsers churning, needs analysis→ Step 4: Retention & Cohorts
Dashboard neededWants visibility for team/investors→ Step 5: Dashboard Design

2. Metrics Framework

Build a metrics system that drives the right behavior. See references/metrics-frameworks.md for complete framework library.

AARRR Pirate Metrics

The universal startup funnel framework:

StageQuestionExample Metrics
AcquisitionHow do users find you?Visitors, signups, CAC by channel
ActivationDo they have a great first experience?Completed onboarding, "aha moment" reached
RetentionDo they come back?DAU/MAU, D1/D7/D30 retention, churn
RevenueDo they pay?Conversion rate, ARPU, LTV
ReferralDo they tell others?NPS, referral rate, viral coefficient

Stage-Appropriate Focus:

StagePrimary FocusWhy
Pre-PMFActivation + RetentionNothing else matters if product doesn't stick
Post-PMFRevenue + AcquisitionTime to scale what works
GrowthAll five, plus efficiencyOptimize the full funnel

North Star Metric

One metric that best captures core value delivered to customers.

Selection Criteria:

  1. Measures value — Correlates with customers getting value
  2. Leading indicator — Predicts future revenue/growth
  3. Actionable — Team can influence it
  4. Simple — Easy to understand and communicate

North Star Examples by Business Model:

ModelNorth StarWhy
B2B SaaSWeekly Active Users, Features UsedValue = engagement with product
MarketplaceTransactions completedBoth sides getting value
SubscriptionWeekly active subscribersRetention predicts LTV
E-commerceRepeat purchase rateLoyalty = sustainable revenue
Usage-basedMonthly usage volumeUsage = revenue
Social/ConsumerDAU/MAU ratioEngagement intensity

Supporting Metrics:

Every North Star needs 3-5 supporting metrics that explain HOW to move it:

North Star: Weekly Active Teams (B2B SaaS)
├── Activation: Teams completing onboarding
├── Engagement: Features used per team
├── Expansion: Seats added per team
└── Retention: Team churn rate

One Metric That Matters (OMTM)

For early-stage focus, pick ONE metric for a defined period:

OMTM Selection:

  1. What's the biggest constraint right now?
  2. What metric would prove that constraint is solved?
  3. Can you move it in 4-8 weeks?

Examples:

  • Pre-launch: "Waitlist signups" (validate demand)
  • Beta: "D7 retention" (validate stickiness)
  • Post-launch: "Activation rate" (validate onboarding)
  • Growth: "Payback period" (validate unit economics)

3. A/B Testing & Experimentation

Run experiments that generate reliable insights. See references/ab-testing.md for templates and calculators.

Experiment Design Framework

Hypothesis Structure:

If we [change], then [metric] will [improve/decrease] by [amount]
because [reason based on user insight].

Example:

If we reduce signup form from 5 fields to 3 fields, then signup completion rate will increase by 15% because user research shows form length is the #1 drop-off reason.

Before Running Any Test

Pre-flight Checklist:

CheckQuestionAction
Sample sizeDo we have enough traffic?Calculate minimum sample (see below)
DurationHow long to reach significance?Usually 1-4 weeks minimum
Metric clarityWhat exactly are we measuring?Define primary + guardrail metrics
Segment impactShould we segment results?Pre-define segments (new vs returning, mobile vs desktop)

Sample Size Estimation:

For 80% power and 95% confidence:

  • 10% baseline, detect 10% relative lift → ~15,000 per variant
  • 10% baseline, detect 20% relative lift → ~4,000 per variant
  • 2% baseline, detect 20% relative lift → ~20,000 per variant

Rule of thumb: Multiply expected traffic by test duration. If you can't reach minimum sample in 4 weeks, the test isn't worth running—make a bigger change.

Running the Test

Test Execution Rules:

  1. Run for full weeks (capture day-of-week effects)
  2. Don't peek early—commit to duration
  3. Track guardrail metrics (what shouldn't break)
  4. Document everything before launch

Guardrail Metrics Examples:

  • Revenue per user (main metric might improve but hurt revenue)
  • Page load time (change might slow performance)
  • Support tickets (change might confuse users)

Interpreting Results

ResultInterpretationAction
Significant winp < 0.05, metric improvedShip it, document learnings
Significant lossp < 0.05, metric declinedDon't ship, learn why
Inconclusivep > 0.05Not enough data OR no real effect
FlatLarge sample, no movementEffect likely too small to matter

Common Pitfalls:

  • Stopping early when results look good (inflates false positives)
  • Testing too many variants (dilutes sample)
  • Ignoring segments (average hides important differences)
  • No hypothesis (test without learning)

4. Retention & Cohort Analysis

Understand if users stick around. See references/retention-cohorts.md for SQL templates and benchmarks.

Retention Fundamentals

Types of Retention:

TypeDefinitionUse When
N-day retention% of users active on exactly day NDaily-use products (social, games)
Bounded retention% active within day range (e.g., week 1)Weekly-use products (SaaS)
Unbounded retention% active on day N or any day afterLong purchase cycles (e-commerce)

Critical Retention Points:

TimeframeWhat It MeasuresHealthy Benchmark
D1First impression>25% (consumer), >40% (B2B)
D7Habit forming>15% (consumer), >30% (B2B)
D30Stickiness>10% (consumer), >25% (B2B)
D90Long-term valueProduct-dependent

Cohort Analysis

Group users by signup date (or other dimension) to track behavior over time.

Cohort Table Structure:

CohortWeek 0Week 1Week 2Week 3Week 4
Jan 1-7100%40%30%25%22%
Jan 8-14100%45%35%28%25%
Jan 15-21100%48%38%32%

Reading Cohort Tables:

  • Rows = Compare cohorts (are newer users retaining better?)
  • Columns = Retention decay (where's the biggest drop-off?)
  • Diagonals = Same calendar week (external events)

Cohort Dimensions Beyond Time:

  • Acquisition channel (organic vs. paid)
  • Plan type (free vs. paid)
  • First action taken (feature X vs. feature Y)
  • Geography

Retention Curves

Healthy Curve Shape:

100% ─┐
      │╲
      │ ╲
      │  ╲____________________  ← Flattens = retention
      │
  0% ─┴─────────────────────────
      D1   D7   D30   D60   D90

Danger Signs:

  • Curve never flattens (continuous bleed)
  • Steep drop after D1 (activation problem)
  • Drop at specific point (feature/billing issue)

Churn Analysis

Churn Rate Calculation:

Monthly Churn = Customers Lost This Month / Customers at Start of Month

Churn Benchmarks (SaaS):

SegmentGoodGreat
SMB<5% monthly<3% monthly
Mid-market<2% monthly<1% monthly
Enterprise<1% monthly<0.5% monthly

Churn Diagnosis Questions:

  1. When do they churn? (Tenure analysis)
  2. Who churns? (Segment analysis)
  3. Why do they churn? (Exit surveys, support tickets)
  4. What predicts churn? (Behavioral signals)

5. Dashboard Design

Create visibility that drives action. See references/dashboard-design.md for templates and tool recommendations.

Dashboard Hierarchy

Level 1: Executive Dashboard (weekly, whole company)

  • 3-5 top-level KPIs
  • Trend vs. target
  • One screen, no scrolling

Level 2: Functional Dashboards (daily, by team)

  • Sales: Pipeline, conversion, activity
  • Product: Engagement, retention, feature adoption
  • Marketing: Acquisition, CAC, channel performance
  • Support: Tickets, response time, CSAT

Level 3: Operational Dashboards (real-time, by function)

  • Engineering: Uptime, latency, errors
  • Sales: Daily activity, quota attainment

KPI Selection

For Each Metric, Answer:

  1. What decision does this inform?
  2. Who needs to see it and how often?
  3. What's the target and why?
  4. What action triggers if it's off-track?

Metric Types to Include:

TypePurposeExample
LeadingPredict future outcomesPipeline, activation rate
LaggingConfirm resultsRevenue, churn
InputActivities you controlCalls made, features shipped
OutputOutcomes you wantDeals closed, retention

Visualization Principles

Choosing Chart Types:

Data TypeBest Chart
Trend over timeLine chart
Comparison across categoriesBar chart
Part-to-wholePie (if <5 segments), stacked bar
DistributionHistogram
CorrelationScatter plot
Funnel stagesFunnel chart

Dashboard Anti-Patterns:

  • ❌ Too many metrics (more than 8-10 per view)
  • ❌ No context (numbers without targets/trends)
  • ❌ Vanity metrics (impressive but not actionable)
  • ❌ Stale data (updated monthly when weekly needed)
  • ❌ No owner (who acts on this?)

Tool Selection

Tool Recommendations by Stage:

StageRecommended Approach
Pre-launchSpreadsheet (Google Sheets)
MVP/BetaSimple analytics (Mixpanel free, Amplitude free, PostHog)
Post-PMFFull stack (Mixpanel/Amplitude + data warehouse + BI tool)
ScalingCustom (Segment → warehouse → Looker/Metabase)

Tool Comparison:

ToolBest ForLimitation
Google AnalyticsWeb traffic, acquisitionWeak on product analytics
MixpanelProduct analytics, funnelsCan get expensive at scale
AmplitudeProduct analytics, cohortsLearning curve
PostHogOpen source, self-hosted optionYounger product
HeapAuto-capture everythingData can be messy
MetabaseSQL-based, self-hosted BIRequires data warehouse
LookerEnterprise BIComplex, expensive

6. Anti-Patterns

Metrics Mistakes:

  • Tracking everything, focusing on nothing
  • Vanity metrics (total signups vs. active users)
  • Lagging-only metrics (revenue without leading indicators)
  • No targets (data without context)

Experimentation Mistakes:

  • Testing small changes on low-traffic pages
  • Multiple changes in one test (can't isolate effect)
  • Stopping tests early based on early results
  • No hypothesis (random changes)

Retention Mistakes:

  • Only looking at aggregate retention (hiding segment issues)
  • Ignoring activation (retention starts at first experience)
  • Not defining "active" clearly

Dashboard Mistakes:

  • Dashboard nobody checks
  • Real-time when weekly is sufficient
  • No owners assigned to metrics

Deliverables

1. Metrics Framework Document

Create as markdown:

  • North Star metric with rationale
  • AARRR funnel with specific metrics
  • Supporting metrics hierarchy
  • Targets and owners

2. Metrics Tracker Spreadsheet

Create using xlsx skill:

  • AARRR funnel metrics with weekly/monthly tracking
  • Formulas for calculated metrics (conversion rates, growth rates)
  • Target vs. actual comparison
  • Charts for trends

3. A/B Test Plan

Create as markdown:

  • Hypothesis statement
  • Variants description
  • Primary and guardrail metrics
  • Sample size and duration calculation
  • Success criteria

4. Cohort Analysis Spreadsheet

Create using xlsx skill:

  • Cohort table (rows = cohorts, columns = time periods)
  • Retention percentages with conditional formatting
  • Retention curve visualization
  • Cohort comparison charts

5. Dashboard Specification

Create as markdown:

  • KPI hierarchy (executive → functional → operational)
  • Metric definitions with formulas
  • Visualization recommendations
  • Data sources and refresh frequency
  • Tool recommendation with rationale

6. SQL Query Templates

Create as markdown:

  • Cohort retention query
  • Funnel conversion query
  • Active user calculation
  • Churn identification query

Reference Files

  • references/metrics-frameworks.md — AARRR deep dive, North Star selection guide, metrics by business model, anti-patterns
  • references/ab-testing.md — Experiment templates, sample size calculator, significance interpretation, SQL queries
  • references/retention-cohorts.md — Cohort methods, retention curves, SQL templates, benchmarks by model
  • references/dashboard-design.md — Dashboard templates, visualization guide, tool comparison

Integration with Other Skills

  • Use business-model skill for unit economics metrics (LTV, CAC, payback)
  • Use product skill for feature prioritization based on analytics
  • Use go-to-market skill for channel-specific acquisition metrics
  • Use operations skill for OKRs aligned with metrics framework
  • Use fundraising skill for investor-ready metrics presentation
  • Use xlsx skill for metrics trackers and cohort spreadsheets
  • Use docx skill for analytics documentation

Adapted from Linas Beliūnas's The One-Person Unicorn founder skill set.

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