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EC315 Confidence Interval Quiz Review

# EC315 Confidence Interval Quiz Review - Quiz Review 1 The...

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Quiz Review 1. The mean number of travel days per year for salespeople employed by hardware distributors needs to be estimated with a 0.90 degree of confidence. For a small pilot study the mean was 150 days and the standard deviation was 14 days. If the population mean is estimated within two days, how many salespeople should be sampled? A: 134 B: 452 C: 511 D: 2100 2. A random sample of 85 group leaders, supervisors, and similar personnel revealed that a person spent an average 6.5 years on the job before being promoted. The standard deviation of the sample was 1.7 years. Using the 0.95 degree of confidence, what is the confidence interval for the population mean? A: 6.99 and 7.99 B: 4.15 and 7.15 C: 6.14 and 6.86 D: 6.49 and 7.49 3. The mean weight of trucks traveling on a particular section of I-475 is not known. A state highway inspector needs an estimate of the mean. He selects a random sample of 49 trucks passing the weighing station and finds the mean is 15.8 tons, with a standard deviation of the sample of 3.8 tons. What is the 95 percent interval for the population mean?

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EC315 Confidence Interval Quiz Review - Quiz Review 1 The...

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