Review with old material
Name____________________________________
1. Harley-Davidson motorcycles make up 14% of all the motorcycles registered in the United States. You plan
to interview an SRS of 500 motorcycle owners. What’s the probability that 20% or more own Harleys?
2. A study found that 48 out of the 200 students surveyed had cheated on a test. Calculate a 90% confidence
interval for the true proportion of student who have cheated on a test.
3. Approximately 82% of all students have copied a classmate’s homework. I have a class of 32.
a. How many do you expect to find have copied?
b.
What is the probability that exactly 28 have copied?
c.
What is the probability that at least 25 have copied?
d.
What is the probability that less than 21 have copied?
4. The number of flaws per square yard in a type of carpet material varies with a mean of 1.8 flaws per
square yard and st. dev. 1.2 flaws. An inspector studies 200 square yards, what the probability that the
mean number of flaws exceeds 2 per square yard?
5. The probability that Ed hits the ball when he goes to bat is 0.23. Find the probability that he doesn’t get a
hit until his 3rd time at bat
6. If I want to estimate the mean SAT score within 5 points with a 99% confidence, how large of a sample
would you need. The standard deviation is 100.
7. The composition of the earth’s atmosphere may have changed over time. The gas in bubbles within amber
should be a sample of the atmosphere at the time the amber was formed. The measures on specimens of
amber are shown below. Construct and interpret a 95% confidence interval for the mean percent of
nitrogen in ancient air.
63.4
65
64.4
63.3
54.8
64.5
60.8
8. Find the mean and standard deviation of the following:
x
p(x)
20
0.02
25
0.03
30
0.08
35
0.12
40
0.22
45
50
0.28
9. I want to test my sweet pea seeds to determine the germination rate, that is the percent of seeds that
sprout. How large of a sample of seeds will I need to be within 4% of the true proportion?
49.1