Chapter 8: Problem 69
What is the point estimator of the population proportion, \(p ?\)
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Chapter 8: Problem 69
What is the point estimator of the population proportion, \(p ?\)
These are the key concepts you need to understand to accurately answer the question.
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For each of the following, find the area in the appropriate tail of the \(t\) distribution. a. \(t=2.467\) and \(d f=28\) b. \(t=-1.672\) and \(d f=58\) c. \(t=-2.670\) and \(n=55\) d. \(t=2.819\) and \(n=23\)
A local gasoline dealership in a small town wants to estimate the average amount of gasoline that people in that town use in a 1-week period. The dealer asked 44 randomly selected customers to keep a diary of their gasoline usage, and this information produced the following data on gas used (in gallons) by these people during a 1-week period. The population standard deviation is not known. \(\begin{array}{rrrrrrrrrrr}23.1 & 13.6 & 25.8 & 10.0 & 7.6 & 18.9 & 26.6 & 23.8 & 12.3 & 15.8 & 21.0 \\ 26.9 & 22.9 & 18.3 & 23.5 & 21.6 & 15.5 & 23.5 & 11.8 & 15.3 & 11.9 & 19.2 \\ 14.5 & 9.6 & 12.1 & 18.0 & 20.6 & 14.2 & 7.1 & 13.2 & 5.3 & 13.1 & 10.9 \\ 10.5 & 5.1 & 5.2 & 6.5 & 8.3 & 10.5 & 7.4 & 7.4 & 5.3 & 10.6 & 13.0\end{array}\) Construct a \(95 \%\) confidence interval for the average weekly gas usage by people in this town.
In a Time/Money Magazine poll of Americans of age 18 years and older, \(65 \%\) agreed with the statement, "We are less sure our children will achieve the American Dream" (Time, October 10,2011 ). Assume that this poll was based on a random sample of 1600 Americans. a. Construct a \(95 \%\) confidence interval for the proportion of all Americans of age 18 years and older who will agree with the aforementioned statement. b. Explain why we need to construct a confidence interval. Why can we not simply say that \(65 \%\) of all Americans of age 18 years and older agree with the aforementioned statement?
A sample of 18 observations taken from a normally distributed population produced the following data: \(\begin{array}{lllllllll}28.4 & 27.3 & 25.5 & 25.5 & 31.1 & 23.0 & 26.3 & 24.6 & 28.4\end{array}\) \(\begin{array}{llllllllll}37.2 & 23.9 & 28.7 & 27.9 & 25.1 & 27.2 & 25.3 & 22.6 & 22.7\end{array}\) a. What is the point estimate of \(\mu\) ? b. Make a \(99 \%\) confidence interval for \(\mu .\) c. What is the margin of error of estimate for \(\mu\) in part b?
At Farmer's Dairy, a machine is set to fill 32 -ounce milk cartons. However, this machine does not put exactly 32 ounces of milk into each carton; the amount varies slightly from carton to carton. It is known that when the machine is working properly, the mean net weight of these cartons is 32 ounces. The standard deviation of the amounts of milk in all such cartons is always equal to \(.15\) ounce. The quality control department takes a sample of 25 such cartons every week, calculates the mean net weight of these cartons, and makes a \(99 \%\) confidence interval for the population mean. If either the upper limit of this confidence interval is greater than \(32.15\) ounces or the lower limit of this confidence interval is less than \(31.85\) ounces, the machine is stopped and adjusted. A recent sample of 25 such cartons produced a mean net weight of \(31.94\) ounces. Based on this sample, will you conclude that the machine needs an adjustment? Assume that the amounts of milk put in all such cartons have a normal distribution.
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