Statistics (Sections 9.1 - 11.1)
Statistics (Sections 9.1 - 11.1)
Statistics (Sections 9.1 - 11.1)
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Solve the problem.<br />
7) In order to set rates, an insurance company is trying to estimate the number of sick days<br />
that full time workers at an auto repair shop take per year. A previous study indicated<br />
that the standard deviation was 2.1 days. a) How large a sample must be selected if the<br />
company wants to be 90% confident that the true mean differs from the sample mean by<br />
no more than 1 day b) Repeat part (a) using a 95% confidence interval. Which level of<br />
confidence requires a larger sample size Explain.<br />
7)<br />
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.<br />
Find the specified t-value.<br />
8) For a t-curve with df = 4, find t 0.05<br />
.<br />
8)<br />
A) 1.645 B) 2.353 C) 2.132 D) 4.604<br />
Solve the problem.<br />
9) Find the critical t-value used for a confidence interval of the mean with a confidence level of 99%<br />
and n = 10.<br />
9)<br />
A) 3.250 B) 2.2821 C) 1.833 D) 2.262<br />
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.<br />
10) Find the critical t-value that corresponds to c = 0.95 and n = 16. (Note; confidence level<br />
written as a decimal = c. So c = 0.95 is the 95% confidence level.)<br />
10)<br />
Find the confidence interval specified.<br />
11) A sociologist develops a test to measure attitudes about public transportation, and 27<br />
randomly selected subjects are given the test. Assume that the population is normally<br />
distributed. The mean score of the sample is 76.2 and the sample standard deviation is<br />
21.4. Construct the 95% confidence interval for the mean score of all such subjects.<br />
11)<br />
12) Construct a 95% confidence interval for the population mean, μ. Assume the population<br />
has a normal distribution. A random sample of 16 fluorescent light bulbs has a mean life of<br />
645 hours with a standard deviation of 31 hours.<br />
12)<br />
Solve the problem.<br />
13) A survey of 250 households showed 19 owned at least one gun. Find a point estimate for<br />
p, the population proportion of households that own at least one gun.<br />
13)<br />
14) In a survey of 10 golfers, 2 were found to be left-handed. Is it practical to construct the<br />
90% confidence interval for the population proportion, p Explain.<br />
14)<br />
15) Many people think that a national lobbyʹs successful fight against gun control legislation is<br />
reflecting the will of a minority of Americans. A random sample of 4000 citizens yielded<br />
2250 who are in favor of gun control legislation. Estimate the true proportion of all<br />
Americans who are in favor of gun control legislation using a 95% confidence interval.<br />
15)<br />
2