The speeds of vehicles traveling on a highway are normally distributed with a population standard deviation of 7 miles per hour and an unknown population mean. If a random sample of 20 vehicles is taken and results in a sample mean of 60 miles per hour, find a 98% confidence interval for the population mean. z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.575 Given: The point estimate is the sample mean, x?, and the margin of error is
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There is concern about the speed of automobiles traveling over a particular stretch of highway. For a random sample of 28 automobiles, radar indicated the following speeds, in miles per hour: $$ \begin{array}{lllllll} 59 & 63 & 68 & 57 & 56 & 71 & 59 \\ 69 & 53 & 58 & 60 & 66 & 51 & 59 \\ 54 & 64 & 58 & 57 & 66 & 61 & 65 \\ 70 & 63 & 65 & 57 & 56 & 61 & 59 \end{array} $$ Assuming a normal population distribution (See Exercise 7.1), find the margin of error of a $95 \%$ confidence interval for the mean speed of all automobiles traveling over this stretch of highway.
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