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Chapter 8: Q.8 (page 477)
Which distribution should you use for this problem?
The distribution is.
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A random survey of enrollment at 35 community colleges across the United States yielded the following figures:
6,414; 1,550; 2,109; 9,350; 21,828; 4,300; 5,944; 5,722; 2,825; 2,044; 5,481; 5,200; 5,853; 2,750; 10,012; 6,357; 27,000;
9,414; 7,681; 3,200; 17,500; 9,200; 7,380; 18,314; 6,557; 13,713; 17,768; 7,493; 2,771; 2,861; 1,263; 7,285; 28,165; 5,080;
11,622. Assume the underlying population is normal.
a. i. = __________
ii. sx = __________
iii. n = __________
iv. n 鈥� 1 = __________
b. Define the random variables X and in words.
c. Which distribution should you use for this problem? Explain your choice.
d. Construct a 95% confidence interval for the population mean enrollment at community colleges in the United
States.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
e. What will happen to the error bound and confidence interval if 500 community colleges were surveyed? Why?
Construct a confidence interval for the population mean hours spent watching television per month.
(a) State the confidence interval
(b) sketch the graph, and
(c) calculate the error bound.
Which distribution should you use for this problem ?
Refer back to the pizza-delivery Try It exercise. The population standard deviation is six minutes and the sample mean delivery time is minutes. Use a sample size of . Find a% confidence interval estimate for the true mean pizza delivery time
Public Policy Polling recently conducted a survey asking adults across the U.S. about music preferences. When asked, of the participants admitted that they have illegally downloaded music.
a. Create a confidence interval for the true proportion of American adults who have illegally downloaded music.
b. This survey was conducted through automated telephone interviews on May and . The error bound of the survey compensates for sampling error, or natural variability among samples. List some factors that could affect the survey鈥檚 outcome that are not covered by the margin of error.
c. Without performing any calculations, describe how the confidence interval would change if the confidence level changed from to .
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