Chapter 7 One Sample Estimation Problems
1. Suppose we want to estimate the average pulse rate of women. A sample of 40 women had a
mean of 76.3 and a standard deviation of 12.5. Construct a 99% confidence interval for the mean
pulse rate of all women.
2. Suppose you want to estimate the average age of UCF students. A sample of 5 students is
selected and the following ages are recorded:
20
18
19
28
18
Find a 95% confidence interval for the average age of all UCF students. Interpret.
3. According to a survey of 800 recent college graduates by MonsterTrak (an online job board for
students) 85% moved back home after graduation. Construct a 96% confidence interval for the
true percentage of all recent college graduates that move back home after graduation.
4. A sociologist wants to estimate the percentage of U.S. households that use e-mail. How many
households must be surveyed to get a margin of error no more than 4% with 95% confidence?
5. Suppose they sampled the amount found in #4 and found that 480 households had used e-mail.
Find a 95% confidence interval for the true percentage of all U.S. households that use e-mail.
6. An estimate is needed of the average age of customers in a department store correct to within 2
years with probability .98. How many customers should be sampled? Assume the ages range
from 15 to 45
7. To estimate the average monthly rent for 1 BDR apartments, 12 complexes are randomly
selected in Orlando. The mean cost is $980 with a standard deviation of $87 Find a 90%
confidence interval for the mean monthly rent,
8. A study is set up to estimate the average weight loss for a new diet plan. How many patients
need to be put on the diet plan to estimate the mean weight loss within 2 pounds with 98%
confidence? Assume σ=6 lbs.
9. Suppose the sample is taken and the average weight loss is found to be 12.6 pounds. Find the
98% confidence interval for the true mean weight loss.
10. How many Americans need to be sampled if we want the confidence interval estimating the
proportion that support abortion rights to have a width of .09 with 95% confidence
11. The sample is taken and it is found that 60% support. Find the 95% confidence interval for the
true proportion that support.
Chapter 8 One Sample Test of Hypotheses
1. Suppose it is claimed the average age of UCF students is 27. To check the claim a sample of
100 students is taken and their average age and standard deviation is calculated.
Is there evidence to suggest the average age is actually less than 27?
a. n  100 s=5 X  26.5
b. n  100 s=5 X  25.5
c. n  100 s=5 X  28.5
2. A car manufacturer claims their new economy model gets an average mpg of at least 58. A
random sample of 36 of these cars yields a mean of 56 with a standard deviation of 6. Is this
evidence to show the claim is too high?
Use  = .01.
3. The company that makes LEGO blocks has certain specifications about their products. One
specification is that the Little People have a neck diameter of .5 inch so that it can be attached
properly to the head. A sample of 30 blocks has an average of .48 inch with a standard
deviation of .05 inch. Test using  = .05.
4. A drug company claims their new pain reliever brings relief in at most 10 minutes. A random
sample of 100 people taking this new pain reliever has a mean relief time of 9.6 minutes with a
standard deviation of 2 minutes. Is there evidence to contradict the claim? Use  = .04.
5.
6.
The mean white blood cell count in adults is 7.5. A company developing a new drug to treat
arthritis pain must check for any side effects. A random sample of 75 patients using the new
drug has a mean of 7.8 and a s.d. of 1.55.
Test to see if there is a problem with the white blood cell count in patients taking the new drug.
Use  =.05
A tobacco company claims its best selling cigarettes contain at most 40 mg of nicotine. A
random sample of 15 of these cigarettes has a mean of 38.5 mg and a standard deviation of 3.7
mg. Is there evidence to support the claim? Use  = .05.
7. Patients who contract a rare disease have only a 2% chance of survival, but a new treatment is being
tested throughout the country. A total of 800 patients have been treated and 35 have survived. Is
there evidence the treatment is effective? Use = .005.
8. In one study of smokers who tried to quit smoking with nicotine patch therapy, 39 were
smoking one year after the treatment and 32 were not smoking one year after the treatment.
Use a .10 significance level to determine if the majority of smokers using the nicotine patch
are smoking one year after treatment.