A quality engineer monitors the manufacture of liquid detergent and wants to assess whether the process is in control. The engineer measures the pH of 25 consecutive batches of detergent.
The engineer creates an I-MR chart to monitor the detergent process.
Interpret the Moving Range chart (MR chart) first to examine the process variation. None of the points are outside the control limits and the points display a random pattern. Thus, the process variation is in control, and the quality engineer can examine the process center on the Individuals chart (I chart).
One observation failed Test 1 on the I chart because the observation is more than 3 standard deviations above the center line.