Chapter 8: Problem 37
What are the parameters of a normal distribution and a \(t\) distribution? Explain.
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Chapter 8: Problem 37
What are the parameters of a normal distribution and a \(t\) distribution? Explain.
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A sample selected from a population gave a sample proportion equal to . 73 . a. Make a \(99 \%\) confidence interval for \(p\) assuming \(n=100\). b. Construct a \(99 \%\) confidence interval for \(p\) assuming \(n=600\) c. Make a \(99 \%\) confidence interval for \(p\) assuming \(n=1500\). d. Does the width of the confidence intervals constructed in parts a through \(\mathrm{c}\) decrease as the sample size increases? If yes, explain why.
The mean time taken to design a house plan by 40 architects was found to be 23 hours with a standard deviation of \(3.75\) hours. a. Construct a \(98 \%\) confidence interval for the population mean \(\mu\). b. Suppose the confidence interval obtained in part a is too wide. How can the width of this interval be reduced? Describe all possible alternatives. Which alternative is the best and why?
A department store manager wants to estimate at a \(90 \%\) confidence level the mean amount spent by all customers at this store. The manager knows that the standard deviation of amounts spent by all customers at this store is \(\$ 31\). What sample size should he choose so that the estimate is within \(\$ 3\) of the population mean?
A researcher wanted to know the percentage of judges who are in favor of the death penalty. He took a random sample of 15 judges and asked them whether or not they favor the death penalty. The responses of these iudges are given here. \(\begin{array}{lllllll}\text { Yes } & \text { No } & \text { Yes } & \text { Yes } & \text { No } & \text { No } & \text { No } & \text { Yes } \\ \text { Yes } & \text { No } & \text { Yes } & \text { Yes } & \text { Yes } & \text { No } & \text { Yes }\end{array}\) a. What is the point estimate of the population proportion? b. Make a \(95 \%\) confidence interval for the percentage of all judges who are in favor of the death penalty.
The following data give the speeds (in miles per hour), as measured by radar, of 10 cars traveling on Interstate \(\mathrm{I}-15\). \(\begin{array}{llllllllll}76 & 72 & 80 & 68 & 76 & 74 & 71 & 78 & 82 & 65\end{array}\) Assuming that the speeds of all cars traveling on this highway have a normal distribution, construct a \(90 \%\) confidence interval for the mean speed of all cars traveling on this highway.
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