16. Box Plots & Statistical Outliers

Box-and-whisker plots summarize continuous distributions without assuming normality. They display the median line, interquartile range (IQR box), whiskers (1.5x IQR), and outlier dots.

Mental Model Intuition

A statistical x-ray of data showing where the middle 50% of values congregate and highlighting extreme anomalies.

Core Concepts & Mechanics

The 5-Number SummaryStatistics

1. Minimum (lower whisker), 2. Q1 (25th percentile), 3. Median (orange line), 4. Q3 (75th percentile), 5. Maximum (upper whisker).

The box height represents the IQR ($Q3 - Q1$). Any point beyond $1.5 \times \text{IQR}$ is plotted as an individual outlier dot.

plt.boxplot(data, patch_artist=True)

`patch_artist=True`Styling

By default, Matplotlib draws boxplots as wireframes. `patch_artist=True` fills the box with solid background color.

Always set `patch_artist=True` to enable modern filled styling.

plt.boxplot(data, patch_artist=True)

Common Beginner Mistakes & Pro Fixes

Avoid the top errors and bad plotting practices that trip up new Python developers

Troubleshooting

Quick Lesson Takeaways

`plt.boxplot()` visualizes median, IQR spread, and outliers.
`patch_artist=True` enables solid filled boxes.
`vert=False` flips the boxplot horizontally.

Topic 16 • Python IDE

Python 3.12 • Matplotlib

Presets:

Ctrl + Enter to run

Run Python code to inspect terminal output.

Real-World Datasets (1-Click Switcher)

Switch from abstract numbers to relatable Cricket, Cinema & Business charts

5 Curated Datasets

Hands-on Challenge: Draw a Box Plot

+50 XP

Write Matplotlib code to solve the objective and see your live plot render

Objective Instructions:

Create a boxplot for `data = [10, 12, 14, 15, 18, 20, 22, 25, 40]` with `patch_artist=True`.

Required Keywords:✓ plt.boxplot✓ patch_artist

Challenge Code Editor

Challenge Output GraphLive Vector Preview

Write code on the left to render live challenge plot

End of Lesson Knowledge Check

Quick Mini Quiz: 2 Concept Questions

Test your understanding to unlock the lesson completion badge

Which Matplotlib function is used to create a standard continuous 2D line plot?

What must you call after specifying label='...' so that the legend actually appears on the canvas?

0 of 2 answered

Pie Charts & Donut Charts

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Violin Plots & Kernel Density