SKILL.md
--- name: data-analyst description: Use when analyzing data for business decisions, designing statistical or ML algorithms, creating data visualizations, or presenting insights to stakeholders. For trend detection, attribution modeling, A/B testing, user segmentation, and executive reporting. --- # Data Analyst Transform data into actionable insights and compelling narratives that drive business decisions. ## Overview This skill combines rigorous statistical methodology with effective data storytelling. It helps you: 1. **Analyze**: Choose and apply the right statistical/ML methods 2. **Design**: Create thresholds, metrics, and decision logic 3. **Communicate**: Present insights that inspire action ## When to Use This Skill - **Algorithm Design**: Designing data analysis algorithms or judgment logic - **Method Selection**: Choosing between statistical tests, regression, or ML methods - **Threshold Design**: Setting decision boundaries or classification criteria - **Trend Analysis**: Detecting changes, growth patterns, or anomalies - **Attribution**: Understanding what drives conversion or outcomes - **Executive Reporting**: Presenting analytics to stakeholders - **A/B Testing**: Designing and interpreting experiments ## Workflow ``` Problem → Classify → Select Method → Design Metrics → Set Thresholds → Tell Story ``` ### Core Methodology **Trend Detection**: - Growth ratio = current_mean / baseline_mean - CV (Coefficient of Variation) for stability - Change point detection for inflection **Statistical Comparison**: | Scenario | Normal Data | Non-Normal | |----------|-------------|------------| | 2 groups | t-test | Mann-Whitney | | 3+ groups | ANOVA | Kruskal-Wallis | **Attribution Models**: - First-touch (awareness) - Last-touch (conversion) - Linear (balanced) - Position-based (40/20/40) - Data-driven (ML) ### Reference Files | File | Content | |------|---------| | `method_selection.md` | Decision tree for all analysis types | | `time_series.md` | St
