Lucia Letter-Carrier, chief analyst for the U.S. Postal Service, will testify before Congress next week on the Service’s parcel delivery efforts. She needs to be concerned about a charge that the delivery time is taking longer. Last year records show that parcels mailed from Washington, D.C. to Los Angeles took an average of 3.1 days. To see if there is any change, a sample of 144 packages mailed from Washington to LA are tracked. The sample shows a mean of 3.3 days and a standard deviation of 1.2. What can you say about the delivery time?
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