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FINAL EXAMINATION
Instruction : Please answer the following questions. All questions carry equal marks.
1. A manufacturer of power tools claims that the mean amount of time required to assemble their top-ofthe-
line table saw is 80 minutes with a standard deviation of 40 minutes. Suppose a random sample of
64 purchasers of this table saw is taken. The probability that the sample mean will be greater than 88
minutes is ________.
TABLE 7-2
The time spent studying by students in the week before final exams follows a normal distribution with a
standard deviation of 8 hours. A random sample of 4 students was taken in order to estimate the mean
study time for the population of all students.
2. Referring to Table 7-2, what is the probability that the sample mean is more than 3 hours below the
population mean?
TABLE 7-5
According to a survey, only 15% of customers who visited the website of a major retail store made a
purchase. Random samples of size 50 are selected.
3. Referring to Table 7-5, the standard deviation of all the sample proportions of customers who will
make a purchase after visiting the website is ________.
TABLE 7-7
Online customer service is a key element to successful online retailing. According to a marketing survey,
37.5% of online customers take advantage of the online customer service. Random samples of 200
customers are selected.
?? Referring to Table 7-7, 95% of the samples proportions symmetrically around the population
proportion will have between ________ % and ________ % of the customers who take advantage of
online customer service.?
TABLE 8-7
A hotel chain wants to estimate the mean number of rooms rented daily in a given month. The population
of rooms rented daily is assumed to be normally distributed for each month with a standard deviation of
24 rooms. During February, a sample of 25 days has a sample mean of 37 rooms.
5. Referring to Table 8-7, the sampling error of a 99% confidence interval for the mean number of
rooms rented daily in a given month is ________.