Is regression still AP Statistics Unit 2?

In the revised 2026–27 CED, regression is Unit 5, with five topics from scatterplots through least-squares regression. Older nine-unit resources use different numbering.

Does a high r² prove a good causal model?

No. r² measures how much response variation is accounted for by the fitted linear relationship in the data. Check residuals, unusual points and study design. A strong association alone does not establish causation.

Which calculator can I use on AP Statistics in 2027?

A graphing calculator with statistical capabilities is expected on both sections. Bluebook includes Desmos graphing. Nongraphing handheld calculators are not allowed in 2027.

AP Statistics

AP Statistics Unit 5 review: Regression Analysis

Unit 5 models relationships between two quantitative variables with correlation and least-squares regression. It is 10–20% of multiple choice in the revised course. Expect to calculate predictions and residuals, interpret slopes with units and judge whether a linear model is appropriate.

Try the practice questions Topic list

By Marteen Tang, founder of Ashore · Updated Nov 9, 2026 · Sources at the bottom of the page

Unit 5 on the May 2027 exam

AP Statistics Unit 5 exam facts
	2027 exam
Weight	10–20% of the multiple-choice section
Exam date	Tuesday, May 11, 2027, afternoon session
Multiple choice	42 questions in 90 minutes, worth 50% of the exam score
Free response	4 questions in 90 minutes, worth 50%. All answers are entered in Bluebook: two multi-focus questions, one inference question and a final multi-focus question.
Calculator	A graphing calculator with statistical capabilities is expected on both sections. Bluebook includes Desmos graphing. Nongraphing handheld calculators are not allowed in 2027.
Class time	About 9 class periods in College Board's pacing guide
2026 results	17% of students scored a 5 on the whole exam, and about 62% scored 3 or higher

Sources: College Board's course and exam description, exam page, 2027 exam dates and score distributions.

What Unit 5 covers

College Board's course description splits the unit into 5 topics. The second column is what you should be able to do for each one.

AP Statistics Unit 5 topics
Topic	What you should be able to do
5.1 Graphical Representations Between Two Quantitative Variables	Describe a scatterplot’s direction, form, strength and unusual points using both variables.
5.2 Correlation	Interpret correlation as the direction and strength of a linear relationship.
5.3 Linear Regression Models	Use a linear model to predict a response and interpret slope and intercept in context.
5.4 Residuals	Calculate observed-minus-predicted residuals and use residual plots to evaluate a model.
5.5 Least-Squares Regression	Explain least squares, derive slope from summary statistics and interpret r².

Read a regression output without losing the context

Let x be the explanatory variable and y the response. A regression prediction is not a guarantee about an individual outcome.

Read a regression output without losing the context
Quantity	Relationship	Interpretation
Predicted response	ŷ = a + bx	Prediction in response-variable units at the given x.
Slope	b = r(sy/sx)	Predicted change in y for one unit increase in x.
Intercept	a = ȳ − bx̄	Predicted y at x = 0; may be outside the useful data range.
Residual	e = y − ŷ	Positive: observed response is above the prediction.
Correlation	−1 ≤ r ≤ 1	Unitless direction and strength of a linear association.
Coefficient of determination	r²	Fraction of sample variation in y accounted for by its fitted linear relationship with x.
Residual pattern	Look for curvature, unequal spread and unusual points	A clear curved pattern signals that a straight line misses structure.

Common mistakes

Each of these loses points on questions you otherwise understand.

Reporting slope as a change without a rate or units. State predicted response change per one explanatory-variable unit. CED printed p. 145.
Explaining a linear pattern only by saying it looks like a line. Describe an approximately constant rate of change and the scatter around the pattern. CED p. 145.
Subtracting observed from predicted for a residual. The convention is observed minus predicted. CED topic 5.4.
Claiming correlation proves causation. A shared explanatory factor or the study design can account for an association. CED topic 5.2.

6 practice questions with answers

Written by Ashore for this page, in the style of the multiple-choice section. Try each one before you open the answer.

Question 1 · 5.3
A model predicts delivery time y in minutes from distance x in km: ŷ = 8 + 2.5x. What is the prediction at x = 6?
- A15 min
- B23 min
- C48 min
- D63 min
Show the answer
B. Substitute x = 6: ŷ = 8 + 2.5(6) = 23 minutes. The 8-minute intercept is added once, not multiplied by distance.
Question 2 · 5.4
At x = 6 km, the model predicts 23 minutes, but the observed delivery takes 27 minutes. What is the residual?
- A−4 min
- B23 min
- C50 min
- D+4 min
Show the answer
D. Residual = observed − predicted = 27 − 23 = +4 minutes. The delivery took four minutes longer than predicted, so the point lies above the fitted line.
Question 3 · 5.5
For a regression of y on x, r = 0.60, sx = 4 and sy = 10. What is the slope?
- A1.5
- B0.24
- C6.0
- D2.4
Show the answer
A. b = r(sy/sx) = 0.60(10/4) = 1.5. Its units are units of y per unit of x. Correlation itself has no units.
Question 4 · 5.5
A least-squares line has slope 1.5 and passes through the sample means x̄ = 8 and ȳ = 20. What is its intercept?
- A12
- B30
- C8
- D−8
Show the answer
C. a = ȳ − bx̄ = 20 − 1.5(8) = 8. A fitted least-squares line with an intercept passes through (x̄, ȳ).
Question 5 · 5.5
A regression has r = −0.80. What percentage of variation in the response is accounted for by the fitted linear model?
- A80%
- B64%
- C−80%
- D20%
Show the answer
B. r² = (−0.80)² = 0.64, so 64% of the variation in the observed response is accounted for by its fitted linear relationship with the explanatory variable. Squaring removes the direction sign.
Question 6 · 5.4
Residuals are mostly positive at low and high x values and mostly negative in the middle. What does this suggest?
- AThe fitted slope must be exactly zero
- BThe correlation must be exactly −1
- CThe response variable has no variability
- DA curved relationship remains after the linear fit
Show the answer
D. The systematic U-shaped pattern means the line underpredicts at the ends and overpredicts in the middle. Residuals from a suitable linear model should not retain this kind of curved structure.

How to study Unit 5

Take a fitted equation and write the slope interpretation with both variable names and units. Calculate one prediction and residual by hand, then check them in the calculator. Ask whether x = 0 is meaningful before interpreting the intercept.

Inspect the scatterplot before using r, and inspect the residual plot after fitting. Compare a point far in the x direction with one far vertically from the line; they can affect a fitted model differently. Keep predictions within the observed x range unless there is a justified model beyond it.

Ashore's Stats course has a lesson and practice questions for every topic in this unit. The free starting check takes about 15 minutes and shows which ones are costing you points.

Questions

Still have a question? support@tryashore.com

It is 10–20% of the multiple-choice section, which is half the exam score. This is not a fixed share of the whole exam: free-response questions can combine units. Suggested pacing is 9 class periods.

By Marteen Tang · Founder of Ashore

Marteen Tang founded Ashore and works on its SAT and AP lessons, practice and plans. Updated Nov 9, 2026.

Sources

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SAT Math · 1 of 5

Calculator allowed

A jacket's price is increased by 20% and then the new price is decreased by 20%. The final price is what percent of the original price?

A $96\%$
B $100\%$
C $104\%$
D $80\%$