sTEm–at-Work Puzzle #38 (Answer)

The data provided not only opens discussion points about the structure of a Run Chart, it provides opportunities to introduce and peruse the least squares analysis of the summarized data chart data provided in the graph's plots.  Since simple linear least squares analysis is available in many data analysis software packages, having students explore this technique is easy.   In many cases, as is in this example, an "eye-ball" linear least squares analysis will do.  The driving criteria for such least squares efforts is to try to construct a line that places the sum of all individual data point distances from the line equal to zero.  This exact task is hard for the eye to accomplish but most people can draw a line that meets this general requirement.  For this example, it should be clear that the least squares line for System 638 is increasing in a steady fashion and indicates  that ( if it has not already done so) the system will produce shear pins that exceed the radius tolerance limit for that part.  Thus, the equipment will need maintenance attention as soon as possible.

The technician decided that system # 638 was not operating as expected. YES