AP Statistics: Part 7 Exam Breakdown
Exam breakdown: Chapters 26-27
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1 Day Test (Wednesday, April 29th)
o 4 Short Answer Questions
Topics to be reviewed:
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Chi-Squared Distribution (Ch. 26)
o Vocabulary to know: Chi-squared Goodness-of-Fit test, Chi-squared Homogeneity
test, Chi-squared Independence test, degrees of freedom
o Know the difference between the three chi-squared tests
 Goodness-of-Fit:
 Degrees of freedom = 𝑛 − 1
 Homogeneity:
 Degrees of freedom = (𝑅 − 1)(𝐶 − 1) where R = # of rows, and C =
# of columns
 Independence:
 Degrees of freedom = (𝑅 − 1)(𝐶 − 1) where R = # of rows, and C =
# of columns
o Conditions for all three chi-squared tests:
 Randomization
 Independence
 Counted data
 Expected cell frequency (only relates to the expected values, not the
observed values)
o Calculator tip: you will get a “domain error” when calculating your p-value if you
enter your observed values as decimals into 𝐿1 . Your expected values can (and
most likely will) be decimals but you need to round your observed values to the
nearest whole number.
Inferences for Regression (Ch. 27)
o Vocabulary to know: regression, association, idealized regression line,
scatterplot, residuals
o Inference for regression test
 Uses t-distribution
 Degrees of freedom = 𝑛 − 2
o Assumptions for regression inference:
 Linearity
 Independence
 Equal variance
 Nearly normal
Don’t forget…
o To list all the conditions IN CONTEXT for hypothesis tests
o To write your hypotheses in words (chi-squared does not use equations for
hypotheses)
o To show ALL WORK (usually a table of observed/expected values!)
o To write out all conclusions IN CONTEXT
Example Short Answer Questions
1.
2.
3. Suppose you were asked to analyze each of the situations described below. (NOTE: DO NOT
ACTUALLY DO THESE PROBLEMS!) For each, indicate which inference procedure you would use
(from the word bank), the test statistic (z, t, or 𝜒 2 ), and if t or 𝜒 2 , the number of degrees of
freedom. You will only use each inference test ONCE and there is one test you will not
use.
Type of Test
Z, t, or 𝝌𝟐
Degrees of Freedom
a
b
c
d
e
f
g
h
Inference Tests:
1-proportion
Matched pairs
Regression inference
2-proportions
1-mean
𝜒 2 G.O.F.
𝜒 2 Independence
2-means
𝜒 2 Independence
a. A researcher wonders if meat in the diet may be a factor in high blood pressure. She
compares the blood pressures of 40 randomly selected vegetarians to those of 40
people who eat meat.
b. According to the American Red Cross, 45% of Americans have Type O Blood, 40% Type
A, 11% Type B, and 4% Type AB. Last week a blood drive at the high school collected 132
pints of blood. If 51 were Type O, 55 Type A, 17 Type B, and 9 were Type AB, was this
yield unusual in any way?
c. Among a random sample of college-age drivers, 5% of the 756 men said they had been
ticketed for speeding during the past year, compared to only 3% of 552 women. Does
this indicate a significant difference between college males and females in terms of
being ticketed for speeding?
d. Who is paid more in New York State – teachers or policemen? We select a random
sample of 25 New York cities and find the starting salaries of teachers and policemen in
each.
e. Researchers offer small cookies to nine nursery school children and record the number
of cookies consumed by each. 45 minutes later they observe these children during
recess and rate each child for hyperactivity on a scale from 1-20. Is there any evidence
that sugar contributes to hyperactivity in children?
f. 22 people complaining of indigestion take an antacid. They report that their discomfort
subsided in an average of 13 minutes; the standard deviation was 4 minutes. The
manufacturer wants a 95% confidence interval for the “relief time”
g. A sports fan selected a random sample of 100 games from each of the NBA, NFL, NHL,
and MLB to see if overtimes (or extra innings) are equally likely to occur in all four
sports.
h. A teacher believes that no more than 10% of high school students ever cheat on an
exam, but a confidential survey found that 14 of 88 randomly selected students
admitted having cheated at least once. Is this strong evidence that the teacher was
wrong?
4.
5.
Part VII Review Book Problems
Directly after the chapter 27 book problems, your textbook contains the Part VII Review
problems. The complete solutions to ALL of these problems can be found under the “Part VII”
tab on the class website: www.myhaikuclass.com/hjhunt/apstats. It is on the side of the page
called “Part VII 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.