Data Visualization Math Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
A pie chart shows 20 slices representing 20 countries' market shares. Explain why this is a poor choice and suggest a better visualization.

Solution

  1. 1
    Problem with many-slice pie chart: humans struggle to compare angles of similar-sized slices; more than 5-7 slices becomes unreadable
  2. 2
    Specific issues: slices close in size look identical; 3D effects distort area perception; no easy way to read exact values
  3. 3
    Better choice: horizontal bar chart — lengths are easy to compare accurately; can sort by value; labels fit naturally
  4. 4
    Alternative: dot plot or treemap for many categories with hierarchical structure

Answer

Pie charts with 20 slices are unreadable. Use a sorted horizontal bar chart instead.
Pie charts are best for 2–5 categories summing to 100%. For many categories, bar charts are far superior — length is easier to judge than angle, sorting by value enables quick ranking, and exact labels can be added.

About Data Visualization

Data visualization is the use of graphs, charts, and other visual representations to communicate patterns, trends, and relationships in data.

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More Data Visualization Examples

Example 1 easy

For the data types listed, choose the most appropriate visualization: (a) one quantitative variable

Example 3 easy

List three features that every well-made graph should have, and explain why each is important.

Example 4 hard

A time series of monthly sales shows both a long-term trend and seasonal fluctuations. Design the id

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