Exercise 8.5.2

Model Answers to 08 ANOVA in Six Sigma Statistics using Minitab 17, Green Belt Edition.

Exercise 8.5.2   Conduct a StDev Test


This time at Evelee golf balls someone has the bright idea that it might also be a good idea to find out if  any of the moulding machines are producing golf balls at different standard deviations.

Analyse the data in File 08 ANOVA.xlsx worksheet Ex 8.5.1 and answer the questions shown below. The data was collected randomly and is recorded in time order.

  1. Is there a difference in populations between the golf ball weights standard deviations produced by any of the moulding machines?
  2. Can the machines be grouped ?
  3. Have the requirements of the test that you have used been met?
  4. Does the Report Card generate any warnings?






Set-Up

Analysis

1. Click Assistant<< Hypothesis Tests

2. Click on One-Way Standard Deviations Test.





2.  Complete the menu as shown and click OK to execute the procedure.


Starting on the top left of the Summary Report, we can conclude that the sample data from the moulding machines is likely to have come from populations where at least one pair of populations had differing weight StDevs.








The Mean Comparison Chart shows us how the moulding machines could be grouped. The Grouping Information Table brings additional clarity.





The Grouping Information Table confirms that in terms of StDevS of weights produced Moulds 1 & 3 can be considered identical and in one group. Moulds 1 & 3 can only be considered different to 5. Moulds 2 & 4 cannot be considered different to any other mould.






The Diagnostic Report for this example is identical to the previous example. There were no issues identified with the previous example.





The Report Card did not show any warnings.