Phase 3: Add Residual Chart Types to SDS Detection

[cnicholas]

Overview

Update the SDS detection system to include residual chart types in the available charts, with proper validation based on sampling design state.

Dependencies

• Phase 1: Create Study Class Foundation
• Phase 2: Implement Study.analyze() Method

Tasks

Step 3.1: Update SDSAnalysisPlan

• Add residual_charts property to each SDS
• SDS 0: No residual charts (no grouping)
• SDS 1/3/4/5: ['R2:S', 'R3:Imr', 'R4:Imr', 'R5:Imr']
• SDS 2/6: ['R2:Imr', 'R3:Imr', 'R4:Imr', 'R5:Imr'] (no S chart possible)

Step 3.2: Update sds_detector.py

• Include R chart in all SDS plans
• Add available_residual_charts() method

Step 3.3: Add chart type validation

• Validate selected chart is appropriate for detected SDS
• Provide clear error messages for invalid selections

Step 3.4: Add residual chart descriptions

• Map chart types to questions answered
• Used in error messages and metadata

Chart Type Reference

Chart Type	Description	Question Answered
R2:S	R2 on S chart	Is unexplained variation stable?
R2:Imr	R2 on XmR chart	Is unexplained variation stable? (SDS 2/6)
R3:Imr	R3 on XmR chart	Is there factor×time interaction?
R4:Imr	R4 on XmR chart	Does time matter?
R5:Imr	R5 on XmR chart	Does the factor matter?

Acceptance Criteria

• study.valid_charts includes residual charts appropriate for the SDS
• SDS 0 has no residual charts
• SDS 2/6 uses R2:Imr instead of R2:S
• Invalid chart selection raises ValueError with helpful message

Estimated Effort

2-3 hours

References

• API_REDESIGN_PLAN.md
• RESIDUAL_CHARTING_PLAN.md