Control Charts

Magnum Magnetics makes induction meters used in vending machines to test the validity of coins. Their specifications require the induction reading capability of the meters to fall between 0.25 and 0.50 Tesla (T) units. Quality analysts took a random test readings of 30 meters (shown below).


  • Using Microsoft Excel® or similar software with statistical capability, construct a run chart from the individual readings.
  • Interpret what the data show. Does the process appear to be in control?
  • What might be some possible causes of different out-of-control indicators?