Discussion:
Q: The manufacturer of the X-15 steel belted radial truck tire claims that the mean mileage the tire can be driven before the treads wear out is 60,000 miles. The standard dev of the mileage is 5,000 miles. The C Truck Company bought 48 tires and found the the mean mileage for their trucks is 59,500 miles. Is C Truck Co's experience different from that claimed by the manufacturer at the .05 significance level?