AP Statistics: Part 2 Exam Breakdown
Exam breakdown: Chapters 7-10
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Day 1
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o
Day 2
o
o
(Tuesday, November 11th)
Ten Multiple Choice Questions
Five Short Answer Questions
(Wednesday, November 12th)
2 AP Multiple Choice Questions
2 AP Free Response Questions
Topics to be reviewed:
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Association and Correlation:
o Explanatory vs. response variables
o Association
 Positive vs. negative association
o Correlation
 A correlation of 0 between two quantitative variables means that
there is no linear association between the two (there can still be
an association, just not linear)
 Correlation ≠ causation (lurking variables)
o Linear Models (AKA: line of best fit, least squares regression line, etc.)
 Know how to create one in your calculator AND by hand
 Be able to: interpret the slope in context, the y-intercept in
context, and the R2 value in context.
 Beware of unusual features: outliers, influential points, high
leverage
 Extrapolation
o Residuals
 If there is a pattern in the residuals plot, then that tells us the
linear model is not appropriate
 Formula: 𝑒 = 𝑦 − 𝑦̂ (AKA: residual = actual – predicted)
 Positive vs. negative residual
Re-expressing Data:
o Four Goals of Re-expressing Data:
 Make the distribution more symmetric
 Make the spread of several groups more alike
 Make the form of a scatterplot more nearly linear
 Make the scatterplot spread out evenly rather than following a fan
shape
o Ladder of Powers
 Know when it is useful to use exponential, logarithmic, and linear
re-expressions
 Know how to re-express data in your calculator (be sure to always
calculate the linear regression line first then plot the residuals and
decide what’s appropriate form there)
Example Multiple Choice Questions
1. All but one of the statements below contain a mistake. Which one could be true?
a. There is a high correlation between cigarette smoking and gender.
b. The correlation between age and weight of a newborn baby is
2.
3.
4.
5.
𝑟 = 0.83 ounces per day.
c. The correlation between a person’s age and vision (20/20) is
𝑟 = −1.04.
d. The correlation between the species of tree and its height is 𝑟 = .56
e. The correlation between blood alcohol level and reaction time is
𝑟 = .73
Which statement about correlation is true?
I. Regression based on data that are summary statistics tends to result in
a higher correlation
II. If 𝑟 2 = .95, the response variable increases as the explanatory variable
increases.
III. An outlier always decreases the correlation.
a. None
b. I only
c. II only
d. III only
e. I, II, and III
Which statement about residuals plot is true?
I. A curved pattern indicates nonlinear association between the variables.
II. A pattern of increasing spread indicates the predicted values become less
reliable as the explanatory variable increases.
III. Randomness in the residuals indicates the model will predict accurately.
a. I only
b. II only
c. I and II only
d. I and III only
e. I, II, and III
Which of A-D is NOT a source of caution in regression analysis between two
variables?
a. Extrapolation
b. Subgroups with different characteristics
c. A lurking variable
d. An outlier
e. all of these are potential problems
Over the past decade a farmer has been able to increase his wheat production by
about the same number of bushels each year. His most useful predictive model is
probably…
a. Exponential
b. Linear
c. Logarithmic
d. Power
e. Quadratic
6. Another farmer has increased his wheat production by about the same percentage
each year. His most useful predictive model is probably…
a. Exponential
b. Linear
c. Logarithmic
d. Power
e. Quadratic
7. The model
can be used to predict the breaking strength of a
rope (in pounds) from its diameter (in inches). According to this model, how much
force should a rope one-half inch in diameter be able to withstand?
a. 4.7 lbs
b. 16 lbs
c. 22 lbs
d. 256 lbs
e. 484 lbs
8. The correlation coefficient between SAT score and ACT score is .675. For a student
with a high SAT score that is 2.3 standard deviations about the mean, we should
expect that student to have an ACT score that is ________ the mean.
a. Equal to
b. 1.2 SD above
c. 1.6 SD above
d. 2.3 SD above
e. .675 SD above
9. When using midterm paper scores to predict a student’s final paper grade in
English class, the student would prefer to have a:
a. Positive residual, because that means the student’s final paper
grade is higher than we predict with the model
b. Positive residual, because that means the student’s final paper
grade is lower than we predict with the model
c. Residual equal to zero, because that means the student’s final
grade is exactly what we would predict with the model
d. Negative residual, because that means the student’s final paper
grade is lower than we predict with the model
e. Negative residual, because that means the student’s final paper
grade is higher than we predict with the model
Example Short Answer Questions
1.
2.
3.
4. Your English teacher found a correlation of .65 between the number of hours of
sleep her students get and their performance on assessments. During the time she
collected data, her students averaged 7 hours of sleep with a standard deviation of
2 hours, and scored an average of 78 on assessments with a standard deviation of
6 points.
a. Create a linear model to estimate the number of points a student will score
on the next exam from the number of hours of sleep they received. Show
your work.
b. If a student sleeps for 8.5 hours, what should the student expect on the next
exam? Show your work.
Part II Review Book Problems
Directly after the chapter 10 book problems, your textbook contains the Part II Review
problems. The complete solutions to ALL of these problems can be found under the
“Part II” tab on the class website: www.myhaikuclass.com/hjhunt/apstats. It is on the
side of the page called “Part II Review Book Solutions”. Here is a breakdown of the
problems and what content each covers. Please focus on the material that you feel you
need the most help/practice in. It’s a good idea to hit each concept but to practice the
content you struggle most with, even more.
AP Questions
Please refer to the FRAPPY problems from the past few weeks to study for that portion
of the test. The complete solutions to these free response questions is also located on
the class website under the “AP Practice” tab on the left side of the website. If you
know the content for chapters 7-10 and can write in context and in full sentences, you
will be fine on the AP free response questions. The AP multiple choice questions are
similar to the multiple choice questions provided on previous pages as well.
Example Multiple Choice Questions – Solutions
1) E 2) B 3) C 4) E 5) B 6) A 7) E 8) C 9) A