Off the Radar: Comparative Evaluation of Radial Visualization Solutions for Composite Indicators

Area of Science:

• Data Visualization
• Human-Computer Interaction
• Information Science

Background:

• Composite indicators (CIs) measure multi-dimensional concepts like ICT usage, requiring effective visualization for understanding.
• Existing CI visualizations lack standardized guidelines, despite the popularity of radial methods due to CI's multi-dimensionality.
• Radar charts are frequently used for CIs, but their empirical effectiveness for common tasks remains unproven.

Purpose of the Study:

• To empirically evaluate the effectiveness and user preference of different radial visualization techniques for composite indicators.
• To compare Radar charts against Flower charts (OECD Betterlife index) and Circle charts for CI presentation.
• To provide evidence-based design guidelines for composite indicator visualization.

Main Methods:

• A controlled experiment was conducted comparing Radar, Flower, and Circle chart visualizations of the same composite indicator data.
• Small multiple views were used to display different data dimensions across the visualization techniques.
• User performance and preference were evaluated against a formal task-taxonomy.

Main Results:

• Radar charts demonstrated the lowest effectiveness and user preference among the tested techniques.
• Flower charts and Circle charts showed mixed performance, task-dependent effectiveness, and a strong user preference for Flower charts.
• Empirical data revealed significant differences in user interaction and perception across the visualization methods.

Conclusions:

• The study provides crucial empirical evidence challenging the widespread use of Radar charts for composite indicators.
• Flower charts emerge as a potentially more effective and preferred alternative for visualizing composite indicator data.
• Specific design guidelines for composite indicator visualization are proposed based on the experimental findings.