Lear Seating of Kitchener, Ontario, produces seats for Cadillacs and other GM cars and trucks. The Cadillac seat includes a part called the EK headrest. The frame of the headrest is made from steel...

Lear Seating of Kitchener, Ontario, produces seats for Cadillacs and other GM cars and trucks. The Cadillac seat includes a part called the EK headrest. The frame of the headrest is made from steel rods. A machine is used to bend the rod into a U-shape described as shown. The width is critical; if it is too wide or too narrow, it will not fit into the holes drilled into the seat frame. The process is checked by drawing samples of size 3 every 2 hours. The last 20 samples were recorded.

a. What do these data tell you about the process? b. If it went out of control, at what sample did this occur? c. What is the likely assignable cause?