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Practice Midterm II

# Practice Midterm II - Practice Midterm II Printable Key...

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Practice Midterm II Printable Key Problem 1 The South Lake Tahoe Police Department has charted the number of arrests over the past twelve months. The number of arrests per month that are made follows a Normal distribution with mean 72 and standard deviation 12 . Construct a control chart and determine any out of control signals. Month 1 2 3 4 5 6 7 8 9 10 11 12 Arrests 61 74 73 98 76 80 110 75 81 100 51 40 Solution Problem 2 Stellar Jay hatchlings have a body weight that is approximately normally distributed with a mean of 3.4 ounces and a standard deviation of 0.3 ounces. A. Convert the following x-intervals into z-intervals. x > 3.0 x < 6.0 Solution B. Convert the following z-interval into an x-interval -1.2 < z < 0.6 Solution Problem 3 Your tire company's snow and mud tires have an average lifetime of 80,000 miles with a standard deviation of 10,000 miles. Answer the following assuming the distribution is normal. A. If the current guarantee for the tires is 65,000 miles, about what percentage of the tires will wear out before the guarantee expires? Solution B. You want to reconsider the guarantee so that about 98% last past the guarantee period. What should you set as the guarantee period on your tires? Solution Problem 4 The Lake Tahoe Visitor's Authority has determined that 65% of the tourists who come to the Lake Tahoe area to go snowboarding are from the Bay area. The Boarder Motel has all of its 35 rooms booked during this weekend. A. What is the probability that between 20 and 25 of the rooms host bay area visitors? Solution

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B. Why is your estimate valid? Solution Problem 5 Explain what the difference is between a sampling distribution and the distribution of a sample. Solution Problem 6 It is know that the mean number of houses a Trick-Or-Treater visits is 46 and the standard deviation is 8 . A. Assuming that the distribution is approximately normal, what is the probability that your seven year old neighbor will visit fewer than 42 houses on Halloween? Solution B. 25 children were randomly selected and observed. What is the probability that their mean number of visits is between 48 and 55 ? Solution Problem 7 Do you favor allowing pilots to carry a gun in the cockpit? 74% of Americans are in favor of allowing pilots to carry a gun in the cockpit. A. 80 passengers board a plane heading toward New York. What is the probability that the greater than 75% of them favor allowing the pilot to carry a gun? Solution B. Is the normal approximation to the proportion p = r/n valid? Explain. Solution Problem 8 The manager of Wasabi restaurant tallied the number of customers that he received over a 50 day period. He found that the mean number per day for this period was 45 with a standard deviation of 8. Construct a 95% confidence interval for the true mean. Write a sentence that explains your findings. Solution
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Practice Midterm II - Practice Midterm II Printable Key...

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