The length of time brake pads last in an automobile varies depending on driving style and the type of car. Brake pads are made from organic, semimetallic, metallic, or synthetic materials, and...

The length of time brake pads last in an automobile varies depending on driving style and the type of car. Brake pads are made from organic, semimetallic, metallic, or synthetic materials, and typically last between 30,000 and 70,000 miles. Independent random samples of cars in for an inspection at dealerships and private garages were obtained and the width (in mm) of the brake pad on the front driver’s side was measured for each. The data are given in the following table.