QC$\mathrm{.}09$ You just got hired as a quality intern for a small startup making $3$D 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?