Scatter Plot & Correlation – AP Statistics | ShowMeClass

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Scatter Plot & Correlation

AP Statistics · Unit 2: Exploring Two-Variable Data

Learning Objectives

Interpret Pearson correlation coefficient r

Identify strength and direction from scatter plots

Distinguish correlation from causation

Recognize the effect of outliers on r

Correlation Formula

Interpreting r

r ≈ ±1: strong linear relationship

|r| ≈ 0.5: moderate relationship

r ≈ 0: no linear relationship

r does NOT imply causation!

CorrelationScatter PlotAP StatsUnit 2

DATASET:

Noise level 0.3

Sample size n 30

Show regression line Show residuals Show 95% ellipse

r (Pearson)—

r²—

n (points)—

slope b—

intercept a—

Interpretation

Try it: click "Custom" then click on the plot to add your own points. Or load a preset dataset and adjust the noise slider.

📝 Quick Quiz▼

1. A correlation of r = −0.85 indicates:

Weak negative relationship Strong positive relationship Strong negative relationship No relationship

2. r² = 0.64 means the regression line explains what % of variance in y?

8% 36% 64% 80%

3. Correlation r is always between:

0 and 1 −1 and 0 −1 and 1 −∞ and ∞