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Chapter 7: Q.45 (page 441)
Decreasing the sample size from to would multiply the standard deviation by
(a) .
(b) .
(c) .
(d) .
(e) none of these.
The correct answer is (b).
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identify the population, the parameter, the sample, and the statistic in each setting
Unemployment Each month, the Current Population Survey interviews a random sample of individuals in about U.S. households. One of their goals is to estimate the national unemployment rate. In December of those interviewed were unemployed
A machine is designed to fill -ounce bottles of shampoo. When the machine is working properly, the mean amount poured into the bottles is ounces with a standard deviation of ounces. Assume that the machine is working properly. If four bottles are randomly selected each hour and the number of ounces in each bottle is measured, then of the observations should occur in which interval?
(a) to ounces
(b) to ounces
(c) to ounces
(d) to ounces
(e) None of the above
AP2.24. Every years, swarms of cicadas emerge from the ground in the eastern United States, live for about six weeks, and then die. (There are several different 鈥渂roods,鈥� so we experience cicada eruptions more often than every years.) There are so many cicadas that their dead bodies can serve as fertilizer and increase plant growth. In a study, a researcher added cicadas under randomly selected plants in a natural plot of American bell flowers on the forest floor, leaving other plants undisturbed. One of the response variables measured was the size of seeds produced by the plants. Here are the box plots and summary statistics of seed mass (in milligrams) for cicada plants and undisturbed (control) plants:
Variable: n Minimum Q1 Median Q3 Maximum
Cicada plants: 39 0.17 0.22 0.25 0.28 0.35
Control plants: 33 0.14 0.19 0.25 0.26 0.29
(a) Is this an observational study or an experiment? Explain.
(b) Based on the graphical displays, which distribution has
the larger mean? Justify your answer.
(c) Do the data support the idea that dead cicadas can
serve as fertilizer? Give graphical and numerical evidence
to support your conclusion.
On a New York鈥搕o鈥揇enver flight, of the passengers were selected for random security screening before boarding. According to the Transportation Security Administration, of passengers at this airport are chosen for random screening.
A large company is interested in improving the efficiency of its customer service and decides to examine the length of the business phone calls made to clients by its sales staff. A cumulative relative frequency graph is shown below from data collected over the past year. According to the graph, the shortest of calls will take how long to complete?
(a) Less than minutes.
(b) At least minutes.
(c) Exactly minutes.
(d) At least minutes.
(e) Less than minutes.
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