c.What is the probability that a simple random sample of 120 customers will have a sample waiting time of less than 3 minutes? 3.Traditionally, 30% of customers of a cell phone company leave after their term contract expires. If this is the true population proportion of churn (customers leaving after their term expired), answer the following questions: (6 Points)a.If simple random samples of 100 customers are taken from the population of customers of this company, describe the sampling distribution of the sample proportion of churn.
b.What is the probability that a simple random sample of 100 customers will have a sample proportion of churn that is within ± 0.03 of the population proportion? c.Check the condition for using the normal distribution to approximate the sampling distribution of the sample proportion and see whether it is valid. 4. A simple random sample of 120 items is taken from an inventory and the average unit cost on the items is $25. The population standard deviation is known to be $10.50. (σ8 Pointsa.Construct a 95% confidence interval for the mean unit cost of the population x± z2 δ√25 ± 1.9610.5√120 = 25± 1.879 = 23.12 to 26.88 ) a n
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- Winter '15