Name: _____________________________________ Date: ___________________________ Period: ______
CHS Statistics
Chapters 19, 21, 23A Review
1.
In the last two months, 94 car occupants were killed by air bags and 61 of those who were killed where
“improperly belted”. Construct a 95% confidence interval estimate of the percentage of car occupants who were killed by air bags while being improperly belted.
2.
Among those who take the Graduate Record Examination (GRE), 67 people are randomly selected. This sample group has a mean score of 558 and a standard deviation of 139 on the quantitative portion of the
GRE. Find a 99% confidence interval estimated of the mean score of all people who took the GRE during that year.
3.
A NAPA Auto Parts supplier wants information about how long car owners plan to keep their cars. A simple random sample of 25 car owners results in a mean of 7.01 years with a standard deviation of 3.74 years. Assume that the sample is drawn from a Normally distributed population. Find a 95% confidence interval estimate of the mean number of years that people plan to keep their cars.

4.
In designing a new machine to be used on an assembly line at a General Motors plant, an engineer obtains measurements of the arm lengths of a random sample of male machine operators. The following values
(in centimeters) are obtained, and the population is normally distributed. Construct the 95% confidence interval for the mean arm length of all such employees.
76.8 75.6 69.3 75.7 75.5 71.2 72.5 71.9
70.9 69.4 71.7 72.5 72.2 68.5 75.9 73.0
5.
In a survey of 1,998 randomly selected adults, 24% included loud commercials among the annoying aspects of television. Construct a 99% confidence interval for the percentage of all adults who are annoyed by loud commercials.

6.
You want to estimate the mean final exam score of all U.S. Statistics students. How many students must you survey if you want 97% confidence that the sample mean is off by no more than 2 points? Assume that a pilot study gave a sample standard deviation(s) of 15.7 points.
7.
In a poll of 1004 adults, 93% indicated that restaurants and bars should refuse service to patrons who have had too much to drink. If you plan to conduct a new poll to confirm that this percentage continues to be correct, how many randomly selected adults must you survey if you want 98% confidence that the margin of error is four percentage points?
8.
What sample size does it take to estimate the outcome of an election with a margin of error of 3%?