Below is a control chart for the strength of pull tests for

Below is a control chart for the strength of pull tests for spot welding on a car assembly line. By looking at this chart, is the process in control? Why? You look at the chart construction data and see that the UCLs and LCLs were determined using subgroup sizes of 3. But the operators are taking subgroup sizes of 5. The operators tell you \"they get better results that way.\" Assess the situation. What do you know about the process? Is it in control or not?

Solution

A)

Undoubtedly the process is out of control.The following are the conditions which decides whether the chart is out of control or not.

1.A single point outside the control limits indicates that the process is out of control.here there is not a single point is out.

2.Two out of three successive points are on the same side of the centerline and farther than 2 from it.here many points are of this type.

3.Four out of five successive points are on the same side of the centerline and farther than 1 from it.

4.A run of eight in a row are on the same side of the centerline.