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A random sample of 15 health maintenance organizations (HMOs) was selected. For each HMO, the co-payment (in dollars) for a doctor's office visit was recorded. The results are as follows. 11, 9, 7, 8, 7, 6, 5, 12, 6, 12, 8, 12, 11, 10, 7 Send data to calculator Under the assumption that co-payment amounts are normally distributed, find a 90% confidence interval for the mean co-payment amount in dollars. Then find the lower limit and upper limit of the 90% confidence interval. Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. (If necessary, consult a list of formulas.) Lower limit: X ? Upper limit: Save For Later Submit Assign