SkillsLib.ai

Experiment Design Assistant for Data Scientists

Design statistically rigorous experiments with preregistration and power analysis

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100+ downloads
Updated Nov 2026

What You Can Do

Design experiments with statistical rigor from the ground up. You'll generate power analyses, create randomization strategies, write preregistration documents, and get AI-assisted reviews of your experimental design to catch biases before data collection. Whether you're planning a clinical trial, A/B test, or academic study, you'll have a complete, defensible experimental protocol.

Features

Power analysis calculator

Determine sample size needed for 80% statistical power with customizable effect sizes and significance levels

Randomization strategy generator

Create stratified, blocked, or clustered randomization schemes tailored to your study design

Preregistration template

Auto-generate Open Science Framework (OSF)-compatible preregistration documents with all required sections

Sample size recommendations

Get quick reference tables for common experimental designs (t-tests, ANOVA, correlation)

Statistical test advisor

Get recommendations on which statistical tests match your hypotheses and experimental structure

Bias detection checklist

Identify selection bias, confounding, measurement bias, and other threats to validity

Hypothesis framework builder

Structure your research questions using the SMART hypothesis framework

Experimental design reviewer

Get detailed feedback on your study design with specific, actionable improvements

Example Output

Power Analysis Output

code
Study: A/B Test on Email Subject Lines
Effect Size (Cohen's d): 0.3 (small-to-medium)
Target Power: 80%
Significance Level (α): 0.05

Sample Size Per Arm: 176
Total Sample Size: 352
Duration: ~4 weeks (assuming 45 conversions/day)

Randomization Schema

code
Method: Stratified Random Assignment
Strata: By user region (US, EU, APAC)
Block Size: 4 (to maintain balance within regions)
Software: Use Python's random.seed(42) or R's blockrand

Assignment Table:
Region | Control | Treatment | Total
US     | 88      | 88        | 176
EU     | 58      | 58        | 116
APAC   | 30      | 30        | 60
TOTAL  | 176     | 176       | 352

Preregistration Snippet (OSF Format)

Study Title: Impact of Subject Line Personalization on Email Open Rates

Primary Hypothesis: Personalized subject lines increase open rates by ≥10% vs. generic lines.

Statistical Test: Two-sample proportion test (χ²)

Analysis Plan: Intent-to-treat analysis with logistic regression controlling for user region and account age.

What's Included

  • SKILL.md: Core experiment design system prompt and workflows
  • Power Analysis Calculator: Template with effect size interpretations and sample size tables
  • Preregistration Template: OSF-ready document covering all 22 AsPredicted.org fields
  • Randomization Strategy Guide: Stratified, blocked, and clustered assignment methods with code examples
  • Bias Detection Checklist: 15-point validity review covering internal, external, construct, and statistical conclusion validity
  • Statistical Test Reference: Quick matrix of tests by hypothesis type (correlation, comparison, regression)
  • Hypothesis Framework Worksheet: SMART hypothesis structure guide

Who It's For

  • Academic researchers designing dissertation studies or journal submissions
  • Data scientists in healthcare and biotech planning clinical or observational studies
  • Product managers and UX researchers designing A/B tests and user experiments
  • Clinical trial coordinators creating protocols that meet regulatory standards
  • Social scientists conducting behavioral experiments or field studies

Best For

  • Planning experiments before data collection — Set up your study design and get feedback before you invest time and resources
  • Calculating sample sizes — Ensure you have enough statistical power to detect your effect of interest
  • Creating randomization procedures — Eliminate selection bias with defensible assignment methods
  • Writing preregistration documents — Meet journal requirements and boost credibility with Open Science practices
  • Reviewing designs for validity threats — Catch confounds, measurement bias, and generalizability issues early

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