Model Answers to 11 Evaluation of Measurement Systems in Six Sigma Statistics using Minitab 17, Green Belt Edition.

Exercise 11.13.1   Gage R&R Crossed

A Gage R&R study has been conducted with 3 operators, 3 repeats and 14 parts. The study does not have a historical StDev or Tolerance. Form a Gage run chart and then conduct the analysis of the Gage R&R Study and then answer the questions shown below.

The data in File 12 MSA.xlsx worksheet Exercise1.

  1. Does the Gage Run Chart indicate any particular types of problem?
  2. How is the measurement system rated?
  3. What is the biggest issue for the study, is it repeatability or reproducibility?
  4. If there are repeatability issues who is causing them?
  5. Are there any other issues?

Set-Up 1

Analysis 1

  1. Click Stat<<Quality Tools<<Gage Study<<Gage Run Chart
  2. Enter the column headings as shown into the main menu.
  3. Click OK to execute the procedure.

Porthos is having repeatability issues. He is probably causing reproducibility issues with the other operators.

I would estimate that repeatability is more of an issue than reproducibility.

Starting on the top left of the Summary Report, the decision bar indicates that the measurement system is unacceptable as it contributes 37.6% of the observed variation.

Set-Up 2

  1. Click Assistant<<Measurement System Analysis
  2. Click on the Gage R&R Study (Crossed) box which is used for continuous data.
  3. The test menu opens. Enter the data columns into the menu as shown.
  4. In the Process Variation section click on the radio button to estimate process variation from parts in the study.
  5. Click OK to execute the procedure.

Analysis 2

The Variation by Source Chart shows that the biggest issue for this study is repeatability.

On the Variation Report the Operator by Part Interaction plot shows Aramis and Athos agree fairly consistently but Porthos’s measurements contain more variation.

The Operator Main Effects plot shows the Porthos’s is measuring at slightly lower average value than the others. The higher spread in his measurement can also be seen.

 The Retest Ranges plot shows the evident repeatability issue shown in terms of measurement range. Porthos had even more problems with part 8.

The study table shows that there was a significant operator part interaction. This means that one or more of the operators ability to measure is dependant upon the part he is measuring.