Question

You just got hired as a quality intern for a small startup making 3D printers. Each printer uses a number of small motors and one of your jobs is to make sure that these motors, received from a small supplier, meet your RPM (revolutions per minute) specifications. The supplier sends you an mean chart (x-bar chart) with each batch of motors to show you that the average RPMs for each batch meets your specifications. Notwithstanding this information from the supplier, you are seeing some unexpected inconsistent performance among the motors within each batch. What should be your first step to help you and the supplier get to the bottom of this issue?

Answer 1

You just got hired as a quality intern for a small startup making 3D printers. Each printer uses a number of small motors and one of your jobs is to make sure that these motors, received from a small supplier, meet your RPM (revolutions per minute) specifications. The supplier sends you an mean chart (x-bar chart) with each batch of motors to show you that the average RPMs for each batch meets your specifications. Notwithstanding this information from the supplier, you are seeing some unexpected inconsistent performance among the motors within each batch. What should be your first step to help you and the supplier get to the bottom of this issue?

A. Make sure the supplier's manufacturing process is capable of meeting your design specifications

B. Instruct the supplier to send you a range chart with each batch and to not send you any more mean charts

C. In addition to a mean chart, have the supplier create and send you a range chart with each batch

D. Have the supplier create and send you a p-chart with each batch so that you can understand what proportion of all motors are bad

Answer:

Option C is correct.

Explanation:

Range chart is also known as a variable control chart which the range of the subgroup is used to establish instantaneous variation and used to evaluate how stable the variability is.