The Chart Selection Guide: Which Chart to Use When

After a chart makeover shows how bad chart choices can distort the story, the next question is which chart to use in the first place. In interviews, this is a favourite because the answer is not about naming a chart from memory; it is about tying the chart choice to the analytical question. This guide shows the question type, best chart, when to use it, when to avoid it, and an Indian example.

The Big Picture: Match the Chart to the Question

Chart selection starts with the question type. Once the question is clear, choose the best chart, explain when to use it, and call out the avoid when condition.

Comparison Questions

For Comparison (few categories), use a Vertical or Horizontal Bar chart when you need to compare 3-8 discrete categories. Avoid it when there are many categories (>10), such as when comparing GMV across 5 e-commerce platforms.

For Comparison (many categories), use a Ranked Horizontal Bar chart. It helps you sort and read long labels easily, such as revenue by 20 product sub-categories; avoid it when there are few categories.

Trend and Distribution Questions

For Trend over Time, use a Line Chart when the question involves a continuous time series, patterns, or seasonality. Avoid it when the X-axis is categorical, such as monthly UPI transaction volume 2021-2025.

For Distribution (one variable), use Histogram / Box Plot when the goal is to show spread, shape, outliers, and percentiles. For example, distribution of Zomato delivery times is a one-variable distribution question; avoid this when comparing across groups simultaneously.

For Distribution (comparison), use Box Plot / Violin Plot to compare distributions of 2-5 groups. For example, delivery time: Bengaluru vs Mumbai vs Delhi is a distribution comparison; avoid this chart choice for a single variable.

Part of Whole, Relationship, and Geographic Questions

For Part of Whole (few parts), use Stacked Bar / Waffle Chart to show composition that adds to 100%. Avoid it when there are many small categories, such as revenue mix: Direct / Channel / Partner.

For Relationship (2 variables), use Scatter Plot for correlation, clusters, and outliers. Avoid it when there are too many points (overplotting), such as ad spend vs conversion rate by campaign.

For Geographic Data, use Choropleth Map / Bubble Map to show regional variation and geographic patterns. Avoid it for precise value comparison, such as state-wise NPS scores for an insurance company.

Funnel, Conversion, and Flow Questions

For Funnel / Conversion, use Funnel Chart / Waterfall when the question is about step-by-step conversion or change. Avoid it for non-sequential data, such as checkout funnel: Cart → Address → Pay → Confirm.

For Flow between Categories, use Sankey Diagram to show flow quantities between states. Avoid it for simple comparisons, such as user journey: Landing page → feature → purchase.

Zomato Example: Distribution vs Distribution Comparison

If the analytical question is the distribution of Zomato delivery times, the question type is Distribution (one variable). The best chart is Histogram / Box Plot because it shows spread, shape, outliers, and percentiles.

If the question changes to delivery time: Bengaluru vs Mumbai vs Delhi, the question type becomes Distribution (comparison). The best chart becomes Box Plot / Violin Plot because it compares distributions of 2-5 groups.

Conclusion

The best chart is the one that matches the analytical question: comparison, trend, distribution, part of whole, relationship, geography, funnel, or flow. In interviews, state the question type first, then name the chart, when to use it, and when to avoid it.