6 Business Statistic questions
All questions must be answered manually— with the aid of a calculator, if necessary.
Question 2 (18 marks)
The general manager of a digital products manufacturer believes that 65% of all potential customers prefer to buy MP3 players with greater than 32 GB built-in memory. A random sample of 100 customers was chosen.
2 BUS B171 Business Statistics
c Suppose that among the 100 customers selected, 58 of them claimed that they prefer to buy MP3 players with over 32 GB built-in memory. Construct a 95% confidence interval estimate for the true proportion of potential customers who prefer to buy MP3 players with greater than 32 GB built-in memory. (6 marks)
Question 3 (15 marks)
The customer services manager of a bank wishes to estimate the true average time it takes for a customer service officer to serve a customer using the dial-in hotline services. A random sample of the service time for 14 individual customers is collected. The results are listed as follows (in minutes):
2.8 1.7 2.2 1.5 2.1 1.9 2.1 1.5 2.0 2.5 1.8 2.4 1.3 2.2
a Construct a 95% confidence interval estimate for the true average time it takes to serve a customer. Keep your final answers to two decimal places. (10 marks)
b Given that the service times are normally distributed and the population variance is known to be 0.25 minutes, what sample size is required if the manager wishes to be 95% confident that the sample average is correct to within 15.0± minutes of the true average service time? (5 marks)
Question 4 (16 marks)
The marketing director of a cosmetics corporation wishes to estimate the average monthly demand for a newly released night-mly selected. Twenty-five of them expressed the
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