Which visualization type is commonly used to display correlations among many variables?

• A. Bar chart
• B. Line chart
• C. Heatmap
• D. Scatter plot

Answer: (C)

Displaying correlations among many variables is most effectively done with a heatmap of a correlation matrix. A heatmap packs all pairwise relationships into a single grid, where each cell shows the strength and direction of the linear relationship between two variables through color. The color gradient makes it quick to spot strong positive or negative associations and, because the matrix is symmetric, patterns emerge that reveal groups of variables with similar correlation structures. This approach scales well to dozens or more variables, unlike scatter plots that require plotting every pair individually and quickly become overwhelming. Bar charts and line charts focus on totals, comparisons, or trends for individual series, not the interconnected relationships across many variables that a correlation heatmap highlights.