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Industrial Statistics with Minitab by Xavier Tort-Martorell Llabres, Lluis Marco Almagro, Pere Grima Cintas

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16.1 Diameter_measure

Parts are manufactured whose critical dimension is a diameter that has specification limits given by 7.5 ± 0.1 mm. To measure this diameter, a micrometer is used with a resolution of up to thousandths of a millimetre.
The company which produces this part uses two standards on the suitability of the measurement process:
  • Standard A: The variability of the measurement system must have a width, measured as 6 standard deviations, of less than 20% of the tolerance interval.
  • Standard B: The variability of the measurement system must have a width, defined as 4 standard deviations, of less than 15% of the tolerance interval.
To verify if either of these rules are met and whether the measurement process is working properly, a sample of 10 parts of recent production is taken and 3 operators measure 3 times each of them in randomorder and without knowing which part they are measuring. The results are stored in file DIAMETER_MEASURE.MTW, in such a way that each row contains the 9 measurements made for each piece:
Column Content
C1 C2-C4 C5-C7 C8-C10 Number of the part measured Measures taken by Carlos of each of the parts Measures taken by Mikel Measures taken by Pablo
Does the measurement system work correctly? Does it meet any of the two above-mentioned standards?

The data are not organized in an appropriate way so that the study can be carried out. ...

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