AP Statistics Scatterplots and Correlation Test with Point Values (PDF)

AP Statistics math test: Scatterplots and Correlation – Maths PDF

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This scatterplots correlation test for AP Statistics covers scatterplots and correlation (Common Core AP STAT 2.4, AP STAT 2.5, HSS-ID.B.6, HSS-ID.C.8, HSS-ID.C.9), with a free PDF to print.

This 45-minute test covers scatterplots, correlation, and the cautions about outliers and causation. Describe plots in context, show every calculation, and justify each conclusion in words.

Time and points

About this test

Grade: AP Statistics
Chapter: Scatterplots and Correlation
Standards: AP STAT 2.4, AP STAT 2.5, HSS-ID.B.6, HSS-ID.C.8, HSS-ID.C.9
Time: 45 minutes
Total: 20 points

Scatterplots correlation test: questions

Question 1 – Describe a scatterplot [4 pts]

Minutes of practice and free throws made.

Describe the association in the scatterplot of practice time and free throws made. (4 points)

Question 2 – Compute r [3 pts]

Five points.

For these five points, x has mean 3 and sd 1.581, y has mean 7.6 and sd 3.209. Compute r from the z-scores. (3 points)

Question 3 – Interpret and units [3 pts]

The correlation between a car’s age and its price is r = -0.91. (a) Interpret r in context. (1 point) (b) If every price is multiplied by 0.9 for a 10% discount, what happens to r? (1 point) (c) Does the correlation show that age lowers price? (1 point)

Question 4 – r and curved data [2 pts]

A scatterplot shows points in a perfect U shape. r = 0.02. A student says the variables are unrelated. Respond.

Question 5 – Outlier effect [2 pts]

A scatterplot of 12 points has r = 0.30. Removing one point near the right end, far below the others, changes r to 0.80. Explain.

Question 6 – Lurking variable [2 pts]

Cities with more firefighters at a fire tend to have more damage. Explain why this does not mean firefighters cause damage.

Question 7 – Match plots [2 pts]

Order r = 0.95, r = -0.2, r = 0, and r = -0.7 from the weakest to the strongest linear association.

Question 8 – Unusual point [2 pts]

A scatterplot with an unusual point.

Identify the unusual point and say whether r is increased or decreased by it compared with the other five points alone.

Key facts behind this scatterplots correlation test

Key facts

Explanatory variable on the x-axis, response variable on the y-axis.
Describe direction, form, strength, and unusual features in context.
-1 <= r <= 1; r near 0 means little linear association, not no association.
r is unitless, unchanged by swapping x and y or by linear changes of units, and not resistant.
Correlation does not imply causation; look for lurking variables.

How to use this scatterplots correlation test

Time yourself: the test is designed for an average student in 45 minutes. Answer the questions you are sure of first, then come back to the longer ones and check your units.

All AP Statistics chapters: AP Statistics math.

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