Applied assessment — control charts and capability

Module quiz

8 questions on Module 4 — Statistical Quality. Answer them all, then check your score before moving on. 6 correct or more is a pass. Your best score is saved on this device, and to your account when you are signed in. This is a self-check, not an accredited assessment.

1. 1. A control chart of a measurement point shows all points inside the limits but eight in a row above the centre line. What does that mean?

   The process is fine because nothing is out of limitsA shift has occurred: a run of eight on one side is a special-cause signal that should be investigated nowThe limits are too wideThe operator recorded the data wrongly

2. 2. Control limits are calculated from what?

   The buyer's toleranceThe process's own measured variationThe factory's target efficiencyThe AQL

3. 3. A process is in control but produces pieces outside the tolerance. What does that tell you?

   The operators are carelessThe process is stable but not capable: the spread is wider than the specification, so the process itself must be changedThe control chart is wrongThe tolerance must be widened

4. 4. Which action is wrong when a point falls inside the control limits but off target?

   Leave the process alone and keep chartingAdjust the machine to bring the next piece back to targetRecord the valueContinue at the set frequency

5. 5. A capability study is run on 20 pieces from one hour of production. Why is that weak?

   Twenty pieces is always too fewOne hour does not include the sources of variation the process sees over shifts, operators, rolls and daysCapability needs at least 500 piecesCapability cannot be measured in garments

6. 6. Measurement error is a large share of the observed variation in your chart. What must you do before acting on the chart?

   Widen the control limitsFix the measurement system first — otherwise the chart mostly plots how you measure, not how you produceIncrease the sample sizeMove to a different chart type

7. 7. What is the practical value of plotting defects per unit over time rather than a monthly total?

   It looks more professionalIt separates a genuine change from normal fluctuation, so you act on signals instead of reacting to every month's numberIt reduces the defect rateIt satisfies the buyer's audit

8. 8. Your process shifts every time a new fabric roll starts. What is the right response?

   Chart the process more oftenTreat roll change as an assignable cause: control it with a setup check and roll-to-roll verification instead of averaging it awayWiden the toleranceStop charting the point