1) A random sample of customer order totals with an average of $78.25 and a population standard deviation of $22.50. Calculate a 90% confidence interval fro the mean, given a sample size of 75 orders
2) A random sample of 35 teenagers averaged 7.3 hours of sleep per night. Assume the population standard deviation is 1.8 hours. Calculate a 98% confidence interval for the mean.
3)A company claims the average time a customer waits for help is 4.78 min. Assume the population standard deviation for wait time is 1.8 min. Test the company claim at the α = 0.05 significance level by comparing the calculated z-score to the critical z-score.