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Chapter 7: Q. 7.1 (page 403)
An unknown distribution has a mean of 45 and a standard deviation of eight. Samples of size are drawn randomly from the population. Find the probability that the sample mean is between and .
the probability that the sample mean is
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Your company has a contract to perform preventive maintenance on thousands of air-conditioners in a large city. Based on service records from previous years, the time that a technician spends servicing a unit averages one hour with a standard deviation of one hour. In the coming week, your company will serve a simple random sample of 70 units in the city. You plan to budget an average of 1.1 hours per technician to complete the work. Will this be enough time?
Use the following information to answer the next six exercises: Yoonie is a personnel manager in a large corporation. Each month she must review 16 of the employees. From past experience, she has found that the reviews take her approximately four hours each to do with a population standard deviation of hours. Let be the random variable representing the time it takes her to complete one review. Assume is normally distributed. Let be the random variable representing the mean time to complete the 16 reviews. Assume that the 16 reviews represent a random set of reviews.
1. What is the mean, standard deviation, and sample size?
Find the probability that the average price for gas stations is less than .
a.
b.
c.
d.
e.
Yoonie is a personnel manager in a large corporation. Each month she must review of the employees. From past experience, she has found that the reviews take her approximately four hours each to do with a population standard deviation of hours. Let Χ be the random variable representing the time it takes her to complete one review. Assume Χ is normally distributed. Let be the random variable representing the meantime to complete the reviews. Assume that the 16 reviews represent a random set of reviews.
Find the probability that the mean of a month’s reviews will take Yoonie from to hrs. Sketch the graph, labeling and scaling the horizontal axis. Shade the region corresponding to the probability.
a.
b. P(________________) = _______
An unknown distribution has a mean of 25 and a standard deviation of six. Let X = one object from this distribution. What is the sample size if the standard deviation of ΣX is 42?
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