Inference Test (Benchmark #3)
On a sheet of paper, number it #1-8.
Your goal is to determine which main
formula/branch you will use to solve
(identifying test type).
• Suppose you have a theory that only children
have higher cholesterol than children who
have siblings. The average cholesterol level
for all Americans is 190. You take a sample of
100 only children and find that their
cholesterol is 198 with a standard deviation of
15. At the 5% significance level, do only
children have significantly higher cholesterol
levels?
• According to an April 2013 CNN Poll, a poll of
1012 people showed that 617 believed that
the U.S. should intervene if North Korea
attacked South Korea. Find a 95% confidence
interval for the true proportion of Americans
who believe that U.S. should intervene if
North Korea attacks South Korea.
• Dr. Raj has invented a new preservative for cut flowers and
wants to test its effectiveness against the leading
commercial preservative. He took two random samples of
100 cut carnations each. One group of flowers was set in
vases containing the new preservative and the other group
was set in vases containing the commercial preservative.
The flowers in the new preservative began to wilt after an
average of 75 hours with a standard deviation of 15 hours.
For the flowers in the commercial preservative the average
was 71 hours with a standard deviation of 10 hours. Is the
data statistically significant evidence that the new
preservative is more effective? Use a 5% significance level.
• A simple random sample of 75 high school
seniors who had after-school jobs showed an
average hourly wage of $8.75 with a standard
deviation of $0.50. Find a 95% confidence
interval for the average hourly wage of all high
school seniors who had after-school jobs.
• (Please respond in sentence form – round to
the nearest cent.)
• If we would like to create a poll with the
following margin of errors, how many people
should our simple random sample contain?
+/- 7%
• The State Fish and Game Division claims that
75% of the fish in the Swatara Creek are
Rainbow Trout. However, the local fishing
club caught and released 189 fish one
weekend and found that 125 were Rainbow
Trout. Does this indicate that the percentage
of Rainbow Trout in the Creek is less than
75%?
• Late-night truck drivers sometimes take an over-thecounter non-prescription drug to keep them from falling
asleep. The main ingredient is caffeine, but too much
caffeine may not be too good for a person’s health. A
random sample of eight truck drivers agreed to have
their pulse rate (beats per minute) measured one-half
hour before and one-half hour after taking such a drug.
The results are shown in the accompanying table. Use a
1% significance level to test the claim that the pulse rate
per minute will be different for all truck drivers taking the
drug.
Driver #
1
2
3
4
5
6
7
8
Before
68
75
110
96
72
80
73
67
After
68
83
110
94
71
85
70
69
• An experiment is conducted investigating the
long-term effects of early childhood intervention
programs (such as head start). In one
(hypothetical) experiment, the high-school drop
out rate of the experimental group (which
attended the early childhood program) and the
control group (which did not) were compared. In
the experimental group, 73 of 85 students
graduated from high school. In the control group,
only 43 of 82 students graduated. Is this
difference statistically significant?