Center

• Mean $\bar{x}$: Arithmetic average; sensitive to outliers
• Median: Middle value; resistant to outliers

Spread

• Range: Max − Min (sensitive to outliers)
• IQR: $Q_3 - Q_1$ (resistant)
• Standard Deviation $s$: Average distance from the mean

Comparing Distributions

When comparing two distributions, always use comparative language:

• "Distribution A has a higher center than Distribution B"
• "Distribution A is more spread out than Distribution B"
• "Both distributions are approximately symmetric"

Five-Number Summary

$\text{Min}, \; Q_1, \; \text{Median}, \; Q_3, \; \text{Max}$

This summary is used to create boxplots. Side-by-side boxplots are excellent for comparing distributions.

AP Tip: On free-response questions, you must use context (mention the actual variable). Don't just say "the distribution is skewed right" — say "the distribution of test scores is skewed right."