# What is the probability that a randomly selected

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Chapter 4 / Exercise 30
Understanding Statistics in the Behavioral Sciences
Pagano Expert Verified
117. What is the probability that a randomly selected cable repair visit falls within 2 standard deviations of the mean? = Difficulty: Hard
Use the following information to answer questions 118-122: Suppose that the waiting time for a license plate renewal at a local office of a state motor vehicle department has been found to be normally distributed with a mean of 30 minutes and a standard deviation of 8 minutes. What is the probability that a randomly selected individual will have a waiting time: 118. Between 15 and 45 minutes
Difficulty: Medium 119. At least 10 minutes
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Chapter 4 / Exercise 30
Understanding Statistics in the Behavioral Sciences
Pagano Expert Verified
P(x≤22) = Difficulty: Hard 121. Suppose that in an effort to provide better service to the public, the director of the local office is permitted to provide discounts to those individuals whose waiting time exceeds a predetermined time. The director decides that 15% of the customers should receive this discount. What are the number of minutes they need to wait to receive the discount? Difficulty: Hard
122. Complete the following statement: Only 20% of the individuals wait less than _____ minutes.
Difficulty: Hard Use the following information to answer questions 123-127: A set of final examination grades in a calculus course was found to be normally distributed with a mean of 69 and a standard deviation of 9. 123. What is the probability of getting a grade of 91 or less on this exam?
Difficulty: Hard 124. What percentage of students scored between 65 and 89?
Difficulty: Medium
125. What percentage of students scored between 81 and 89?
.4868-.4332=.0536 Difficulty: Medium 126. Only 5% of the students taking the test scored higher than what grade? Difficulty: Hard
127. A manufacturer of personal computers sets tests competing brands and finds that the amounts of energy they require are normally distributed with a mean of 285 kwh and a standard deviation of 9.1 kwh. If the lowest 25% and the highest 30% are not included in a second round of tests, what are the upper and lower limits for the energy amounts of the remaining sets? Difficulty: Hard
Use the following information to answer questions 128-132: While conducting experiments, a marine biologist selects water depths from a uniformly distributed collection that vary between 2.00 m and 7.00 m. 128. What is the probability that a randomly selected depth is less than 3.60 m? Difficulty: Easy
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