Ab Testing
Corey HainesCommunityCreated by Corey Haines
- Skill
- Guidelines
- Business and productivity
- MIT
- No issues found
AutoGineer summary
Written by AutoGineer from the skill’s own files, not by the author
This skill provides a structured approach to experimentation, moving beyond simple testing to building a systematic growth engine. It covers the entire lifecycle of an experiment, from hypothesis generation and ICE prioritization to statistical analysis and documentation. It emphasizes statistical rigor, clear hypothesis formulation, and the importance of maintaining an experiment playbook to compound learnings over time.
What it does
- Guides the creation of testable hypotheses using a structured framework.
- Provides reference tables for calculating sample sizes and test durations.
- Offers templates for test planning, results documentation, and experiment repositories.
- Defines best practices for traffic allocation and variant design.
- Outlines a systematic process for running a continuous growth experimentation program.
- Explains how to interpret statistical significance and handle common testing pitfalls.
When to use it
- When you need to compare two approaches to determine which performs better.
- When designing a new A/B, multivariate, or split-URL test.
- When you want to establish a repeatable, data-driven experimentation practice.
- When you need to prioritize growth experiments using the ICE scoring method.
- When you need to document test results and learnings for future reference.
Advantages
- Promotes statistical rigor to prevent false positives and incorrect business decisions.
- Standardizes the experimentation process across teams with clear templates.
- Helps build a library of proven growth patterns through a structured playbook.
- Reduces guesswork by grounding experiments in data and clear hypotheses.
- Provides actionable guidance on common challenges like sample size and peeking.
Usage examples
- “I want to test if changing our CTA button color increases signups. How should I structure this?”
- The agent will guide you through defining a hypothesis, selecting primary/secondary metrics, calculating the required sample size, and setting up the test design.
- “How do I prioritize our backlog of growth experiments?”
- The agent will explain the ICE (Impact, Confidence, Ease) scoring framework and how to apply it to rank your experiments.
- “We finished an A/B test. How should we document the results?”
- The agent will provide a results documentation template to capture sample sizes, metric performance, statistical significance, and key learnings.
- “How long should I run this experiment to get valid results?”
- The agent will help you calculate the required sample size based on your baseline conversion and MDE, and determine the necessary duration based on your traffic.
Install
Download the skill as a ZIP:
https://autogineer.com/agent-skills/coreyhaines31/ab-testing/downloadUnzip it into the cross-client skills folder of your project:
mkdir -p .agents/skills && unzip ab-testing.zip -d .agents/skills
Documentation by Corey Haines
A/B Test Setup
You are an expert in experimentation and A/B testing. Your goal is to help design tests that produce statistically valid, actionable results.
Initial Assessment
Check for product marketing context first:
If .agents/product-marketing.md exists (or .claude/product-marketing.md, or the legacy product-marketing-context.md filename, in older setups), read it before asking questions. Use that context and only ask for information not already covered or specific to this task.
Before designing a test, understand:
Test Context - What are you trying to improve? What change are you considering?
Current State - Baseline conversion rate? Current traffic volume?
Constraints - Technical complexity? Timeline? Tools available?
Core Principles
1. Start with a Hypothesis
Not just "let's see what happens"
Specific prediction of outcome
Based on reasoning or data
2. Test One Thing
Single variable per test
Otherwise you don't know what worked
3. Statistical Rigor
Pre-determine sample size
Don't peek and stop early
Commit to the methodology
4. Measure What Matters
Primary metric tied to business value
Secondary metrics for context
Guardrail metrics to prevent harm
Hypothesis Framework
Structure
Because [observation/data],
we believe [change]
will cause [expected outcome]
for [audience].
We'll know this is true when [metrics].Example
Weak: "Changing the button color might increase clicks."
Strong: "Because users report difficulty finding the CTA (per heatmaps and feedback), we believe making the button larger and using contrasting color will increase CTA clicks by 15%+ for new visitors. We'll measure click-through rate from page view to signup start."
Test Types
| Type | Description | Traffic Needed |
|---|---|---|
| A/B | Two versions, single change | Moderate |
| A/B/n | Multiple variants | Higher |
| MVT | Multiple changes in combinations | Very high |
| Split URL | Different URLs for variants | Moderate |
Sample Size
Quick Reference
| Baseline | 10% Lift | 20% Lift | 50% Lift |
|---|---|---|---|
| 1% | 160k/variant | 43k/variant | 7.7k/variant |
| 3% | 53k/variant | 14k/variant | 2.5k/variant |
| 5% | 31k/variant | 8.2k/variant | 1.5k/variant |
| 10% | 15k/variant | 3.8k/variant | 690/variant |
Per variant, for 95% confidence (two-sided) and 80% power. Lift is relative (3% → 3.6% is a 20% lift).
Calculators:
For detailed sample size tables and duration calculations: See references/sample-size-guide.md
Metrics Selection
Primary Metric
Single metric that matters most
Directly tied to hypothesis
What you'll use to call the test
Secondary Metrics
Support primary metric interpretation
Explain why/how the change worked
Guardrail Metrics
Things that shouldn't get worse
Stop test if significantly negative
Example: Pricing Page Test
Primary: Plan selection rate
Secondary: Time on page, plan distribution
Guardrail: Support tickets, refund rate
Opt-In Elements: Measure the Exposed Group
When a change only reaches visitors who interact with it (a hero video, a calculator, a chat widget), a test on overall conversion is underpowered: if 10% of visitors click play, the other 90% add noise and no signal. Either run a triggered analysis (log the same trigger point in both arms, such as the play button coming into view, and compare only visitors who reached it; don't filter on clicks, since the variant can change who clicks), or skip the test, ship the better version, and compare versions on engagement (watch-through) and viewer conversion, tagged by version ID. The second is a directional comparison, not a controlled test.
Designing Variants
What to Vary
| Category | Examples |
|---|---|
| Headlines/Copy | Message angle, value prop, specificity, tone |
| Visual Design | Layout, color, images, hierarchy |
| CTA | Button copy, size, placement, number |
| Content | Information included, order, amount, social proof |
Best Practices
Single, meaningful change
Bold enough to make a difference
True to the hypothesis
Traffic Allocation
| Approach | Split | When to Use |
|---|---|---|
| Standard | 50/50 | Default for A/B |
| Conservative | 90/10, 80/20 | Limit risk of bad variant |
| Ramping | Start small, increase | Technical risk mitigation |
Considerations:
Consistency: Users see same variant on return
Balanced exposure across time of day/week
Implementation
Client-Side
JavaScript modifies page after load
Quick to implement, can cause flicker
Tools: PostHog, Optimizely, VWO
Server-Side
Variant determined before render
No flicker, requires dev work
Tools: PostHog, LaunchDarkly, Split
Running the Test
Pre-Launch Checklist
[ ] Hypothesis documented
[ ] Primary metric defined
[ ] Sample size calculated
[ ] Variants implemented correctly
[ ] Tracking verified
[ ] QA completed on all variants
During the Test
DO:
Monitor for technical issues
Check segment quality
Document external factors
Avoid:
Peek at results and stop early
Make changes to variants
Add traffic from new sources
The Peeking Problem
Looking at results before reaching sample size and stopping early leads to false positives and wrong decisions. Pre-commit to sample size and trust the process.
Analyzing Results
Statistical Significance
For a pre-specified fixed-horizon test, compare its p-value with the chosen significance level (commonly α = 0.05).
A p-value describes how incompatible the data are with the null model: the probability, assuming that model and its assumptions, of a result at least as extreme as the observed one. It is not the probability that the result is random, that the null is true, or that a variant will win again.
A 95% confidence interval comes from a procedure with 95% coverage over repeated samples under its assumptions. It is not a 95% posterior probability that this particular interval contains the true effect. Report the interval and effect size alongside the p-value.
Use the planned analysis and stopping rule. Sequential tests and Bayesian analyses have their own interpretation; do not translate every platform's “confidence” score into a fixed-horizon p-value.
These distinctions follow the American Statistical Association's p-value statement. Statistical significance alone does not establish business value or justify shipping a variant.
Analysis Checklist
Reach sample size? If not, result is preliminary
Statistically significant? Check confidence intervals
Effect size meaningful? Compare to MDE, project impact
Secondary metrics consistent? Support the primary?
Guardrail concerns? Anything get worse?
Segment differences? Mobile vs. desktop? New vs. returning?
Interpreting Results
| Result | Conclusion |
|---|---|
| Significant winner | Check effect size, uncertainty and guardrails before implementing |
| Significant loser | Keep control, learn why |
| No significant difference | Report the effect interval: it may still allow meaningful benefit and harm, or may exclude effects worth pursuing. Follow the planned stopping rule; do not extend a finished fixed-horizon test until it becomes significant. Plan a new test if needed. |
| Mixed signals | Check data quality and planned metrics; label unplanned segment findings exploratory and confirm them in a new test |
Documentation
Document every test with:
Hypothesis
Variants (with screenshots)
Results (sample, metrics, significance)
Decision and learnings
For templates: See references/test-templates.md
Growth Experimentation Program
Individual tests are valuable. A continuous experimentation program is a compounding asset. This section covers how to run experiments as an ongoing growth engine, not just one-off tests.
The Experiment Loop
1. Generate hypotheses (from data, research, competitors, customer feedback)
2. Prioritize with ICE scoring
3. Design and run the test
4. Analyze results with statistical rigor
5. Promote winners to a playbook
6. Generate new hypotheses from learnings
→ RepeatHypothesis Generation
Feed your experiment backlog from multiple sources:
| Source | What to Look For |
|---|---|
| Analytics | Drop-off points, low-converting pages, underperforming segments |
| Customer research | Pain points, confusion, unmet expectations |
| Competitor analysis | Features, messaging, or UX patterns they use that you don't |
| Support tickets | Recurring questions or complaints about conversion flows |
| Heatmaps/recordings | Where users hesitate, rage-click, or abandon |
| Past experiments | "Significant loser" tests often reveal new angles to try |
ICE Prioritization
Score each hypothesis 1-10 on three dimensions:
| Dimension | Question |
|---|---|
| Impact | If this works, how much will it move the primary metric? |
| Confidence | How sure are we this will work? (Based on data, not gut.) |
| Ease | How fast and cheap can we ship and measure this? |
ICE Score = (Impact + Confidence + Ease) / 3
Run highest-scoring experiments first. Re-score monthly as context changes.
Experiment Velocity
Track your experimentation rate as a leading indicator of growth:
| Metric | Target |
|---|---|
| Experiments launched per month | 4-8 for most teams |
| Win rate | 20-30% is common for mature programs (sustained higher rates may indicate conservative hypotheses) |
| Average test duration | 2-4 weeks |
| Backlog depth | 20+ hypotheses queued |
| Cumulative lift | Compound gains from all winners |
The Experiment Playbook
When a test wins, don't just implement it — document the pattern:
## [Experiment Name]
**Date**: [date]
**Hypothesis**: [the hypothesis]
**Sample size**: [n per variant]
**Result**: [winner/loser/inconclusive] — [primary metric] changed by [X%] (95% CI: [range], p=[value])
**Guardrails**: [any guardrail metrics and their outcomes]
**Segment deltas**: [notable differences by device, segment, or cohort]
**Why it worked/failed**: [analysis]
**Pattern**: [the reusable insight — e.g., "social proof near pricing CTAs increases plan selection"]
**Apply to**: [other pages/flows where this pattern might work]
**Status**: [implemented / parked / needs follow-up test]Over time, your playbook becomes a library of proven growth patterns specific to your product and audience.
Experiment Cadence
Weekly (30 min): Review running experiments for technical issues and guardrail metrics. Don't call winners early — but do stop tests where guardrails are significantly negative.
Bi-weekly: Conclude completed experiments. Analyze results, update playbook, launch next experiment from backlog.
Monthly (1 hour): Review experiment velocity, win rate, cumulative lift. Replenish hypothesis backlog. Re-prioritize with ICE.
Quarterly: Audit the playbook. Which patterns have been applied broadly? Which winning patterns haven't been scaled yet? What areas of the funnel are under-tested?
Common Mistakes
Test Design
Testing too small a change (undetectable)
Testing too many things (can't isolate)
No clear hypothesis
Execution
Stopping early
Changing things mid-test
Not checking implementation
Analysis
Ignoring confidence intervals
Cherry-picking segments
Over-interpreting inconclusive results
Task-Specific Questions
What's your current conversion rate?
How much traffic does this page get?
What change are you considering and why?
What's the smallest improvement worth detecting?
What tools do you have for testing?
Have you tested this area before?
Related Skills
cro: For generating test ideas based on CRO principles
analytics: For setting up test measurement
copywriting: For creating variant copy
Files
- ATTRIBUTION.mdAdded by AutoGineer881 B
- LICENSELicence file added by AutoGineer1.0 KiB
- SKILL.md13.0 KiB
- evals/evals.json8.8 KiB
- references/sample-size-guide.md9.0 KiB
- references/test-templates.md6.3 KiB
evals/evals.json
{
"skill_name": "ab-testing",
"evals": [
{
"id": 1,
"prompt": "I want to A/B test our homepage headline. We currently say 'The All-in-One Project Management Tool' and want to test something benefit-focused. We get about 15,000 visitors/month and our current signup rate is 3.2%.",
"expected_output": "Should check for product-marketing.md first. Should build a proper hypothesis using the framework: 'Because [observation], we believe [change] will cause [outcome], which we'll measure by [metric].' Should identify this as an A/B test (two variants). Should calculate or reference sample size needs based on 15,000 monthly visitors and 3.2% baseline. Should define primary metric (signup rate), secondary metrics, and guardrail metrics. Should warn about the peeking problem and recommend a fixed test duration. Should provide the test plan in the structured output format.",
"assertions": [
"Checks for product-marketing.md",
"Uses the hypothesis framework with observation, belief, outcome, and metric",
"Identifies as A/B test type",
"Addresses sample size calculation based on traffic and baseline rate",
"Defines primary metric (signup rate)",
"Defines secondary and guardrail metrics",
"Warns about the peeking problem",
"Provides structured test plan output"
],
"files": []
},
{
"id": 2,
"prompt": "we want to test like 4 different CTA button colors on our pricing page. is that a good idea?",
"expected_output": "Should trigger on casual phrasing. Should identify this as an A/B/n test (multiple variants). Should caution that testing 4 variants requires significantly more traffic than a simple A/B test. Should reference the sample size quick reference showing traffic multipliers for multiple variants. Should question whether button color alone is likely to produce meaningful lift vs testing CTA copy, placement, or surrounding context. Should recommend either reducing to 2 variants or ensuring sufficient traffic. Should still provide hypothesis framework and test setup if proceeding.",
"assertions": [
"Triggers on casual phrasing",
"Identifies as A/B/n test (multiple variants)",
"Cautions about increased traffic needs for 4 variants",
"References sample size requirements",
"Questions whether button color alone is high-impact",
"Suggests alternative higher-impact elements to test",
"Provides hypothesis framework"
],
"files": []
},
{
"id": 3,
"prompt": "Our test has been running for 3 days and Variant B is winning with 95% confidence. Should we call it?",
"expected_output": "Should immediately address the peeking problem. Should explain that checking results early inflates false positive rates. Should recommend running for the full pre-calculated duration regardless of early results. Should explain why early significance can be misleading (regression to the mean, day-of-week effects, audience mix shifts). Should provide guidance on when it IS appropriate to stop early (sequential testing methods). Should recommend the pre-test commitment to duration.",
"assertions": [
"Addresses the peeking problem directly",
"Explains why early significance is misleading",
"Recommends running for full pre-calculated duration",
"Mentions day-of-week effects or audience mix shifts",
"Explains false positive rate inflation from peeking",
"Mentions sequential testing as alternative approach"
],
"files": []
},
{
"id": 4,
"prompt": "Help me set up a multivariate test on our landing page. I want to test the headline, hero image, and CTA button simultaneously.",
"expected_output": "Should identify this as a Multivariate Test (MVT). Should explain that MVT tests combinations of elements and requires much more traffic than A/B tests. Should calculate or reference traffic needs (combinations multiply: e.g., 2 headlines × 2 images × 2 CTAs = 8 combinations). Should recommend MVT only if traffic supports it, otherwise suggest sequential A/B tests. Should build hypotheses for each element being tested. Should define interaction effects to watch for. Should provide structured test plan.",
"assertions": [
"Identifies as multivariate test (MVT)",
"Explains MVT tests combinations of elements",
"Addresses dramatically higher traffic requirements",
"Calculates number of combinations",
"Suggests sequential A/B tests as alternative if traffic insufficient",
"Builds hypotheses for each element",
"Provides structured test plan"
],
"files": []
},
{
"id": 5,
"prompt": "What metrics should I track for an A/B test on our trial signup page? We're testing a longer form (adds company size and role fields) against the current short form.",
"expected_output": "Should apply the metrics selection framework with three tiers: primary, secondary, and guardrail metrics. Primary: form completion rate (the direct conversion metric). Secondary: lead quality metrics (SQL conversion rate, activation rate post-signup). Guardrail: overall signup volume (ensure longer form doesn't tank total signups below acceptable threshold). Should explain the tradeoff between conversion quantity and lead quality. Should note that this test needs longer observation window to measure downstream metrics.",
"assertions": [
"Applies three-tier metric framework (primary, secondary, guardrail)",
"Identifies form completion rate as primary metric",
"Identifies lead quality as secondary metric",
"Defines guardrail metrics to protect against negative outcomes",
"Explains quantity vs quality tradeoff",
"Notes need for longer observation window for downstream metrics"
],
"files": []
},
{
"id": 6,
"prompt": "Can you help me write copy for our new landing page? We want to test it against the current version.",
"expected_output": "Should recognize this is primarily a copywriting task, not a test setup task. Should defer to or cross-reference the copywriting skill for writing the actual copy. May help frame the test hypothesis and setup, but should make clear that copywriting is the right skill for creating the page copy itself.",
"assertions": [
"Recognizes this as primarily a copywriting task",
"References or defers to copywriting skill",
"Does not attempt to write full page copy using test setup patterns",
"May offer to help with test hypothesis and setup"
],
"files": []
},
{
"id": 7,
"prompt": "We ran an A/B test on our pricing page for 4 weeks. Control: 2.1% conversion. Variant: 2.4% conversion. 12,000 visitors per variant. Is this statistically significant? Should we ship it?",
"expected_output": "Should calculate the result under a declared analysis: 252/12,000 vs 288/12,000 gives approximately p = 0.117 for an uncorrected two-sided pooled-proportion z-test, so it does not meet alpha = 0.05. Should distinguish the 0.3 percentage-point / ~14% relative estimate from evidence for a reliably positive effect. Report uncertainty and practical business impact. Respect the pre-specified duration and stopping rule; do not recommend continuing the completed fixed-horizon test until significant. Unplanned segments are exploratory; a follow-up test needs its own plan.",
"assertions": [
"Uses actual conversion counts and states the analysis assumptions",
"Does not call p ~0.117 significant at alpha = 0.05",
"Distinguishes statistical uncertainty from business value",
"Does not extend a completed fixed-horizon test until significant",
"Labels unplanned segment findings exploratory"
],
"files": []
},
{
"id": 8,
"prompt": "Our fixed-horizon A/B test reached its planned sample today with p = 0.04. Can I tell the CEO there is a 96% chance the change works and just a 4% chance the lift was random? We have a +2% estimate, an interval of +0.1% to +3.9%, and a higher refund rate in the variant.",
"expected_output": "Reject both probability interpretations. Explain the p-value conditional on the null model and assumptions, and repeated-sampling interval coverage without asserting a posterior probability. Consider the effect interval, practical impact and refund guardrail before recommending rollout. Do not substitute a numerical significance threshold for the business decision.",
"assertions": [
"Does not interpret 1-p as the probability the variant works",
"Does not interpret p as the probability the result was random",
"Explains the conditional null-model meaning",
"Uses interval, business effect and refund guardrail before rollout"
],
"files": []
}
]
}
Requirements and compatibility
Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta
“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.
Security
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Attribution and licence
- Created by
- Corey Haines
- Publisher
- Corey Haines (Community)
- Source
- coreyhaines31/marketingskills · skills/ab-testing · commit 96798cf
- Licence
- MIT License (redistribution allowed)
- LICENSE (added by AutoGineer from LICENSE)
- ATTRIBUTION.md (written by AutoGineer)
- Synced
AutoGineer is not affiliated with or endorsed by Corey Haines or Corey Haines.
Download ZIP
The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download ab-testing.zip