Econ 375 Chapter 8 Questions Problem Computer Services, Inc. wants to determine

Question

Econ 375 Chapter 8 Questions Problem Computer Services, Inc. wants to determine a confidence interval for the average CPU time of t teleprocessing transactions. A sample of 64 transactions yielded a mean of 6 seconds with a standard deviation of 0.8 seconds. Determine a 98% confidence interval for the average CPU time. heir 1. 2. Six hundred consumers were asked whether they would like to purchase a domestic or a foreign automobile. Their responses are given below. Preference Domestic Foreign Frequency 240 360 Develop a 95% confidence interval for the proportion of all consumers who prefer to purchase domestic automobiles. 3. A local electronics firm wants to determine their average daily sales (in dollars.) A sample of the sales days revealed average sales of $139,000. Assume that the standard deviation of the population is known to be $12,000. a. b. Provide a 95% confidence interval estimate for the average daily sales. Provide a 97% confidence interval estimate for the average daily sales.

Explanation / Answer

1)

we know that the confidence interval is given as

Mean +- z*sd/sqrt(n)

here z = 1.96 for 95%ci from the z table
mean = 6
sd =0.8
n = 64

putting the values

6 +- 1.96*0.8/sqrt(64)

solving for plus and minus sign

we get the interval as
Lower bound
6 - 1.96*0.8/sqrt(64) = 5.804

Upper bound
6 + 1.96*0.8/sqrt(64) = 6.196

Please note that we can answer only 1 question at a time , as er the answering guidelines

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