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

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14.7 Capability Study when the Sample Size Is Equal to One

14.7.1 Values Taken at Regular Intervals of Time

Example 14.1:
A company produces dry food for dogs and uses an extrusion process where the product humidity is a relevant characteristic of quality. To carry out a capability study of the humidity variable, which value must be between 6% and 12%, a one unit sample is taken every 15 minutes and subsequently a measure of the humidity is recorded. Samples are taken during 8 hours obtaining the following 32 humidity measures (entered by rows, order is important):
Unnumbered Table

Place the data values in a column named Humidity, and go to:

Stat > Quality Tools > Capability Analysis > Normal, and indicate that the data is contained in the column Humidity, that the subgroup size (sample size) is 1, and that the specification limits are 6 and 12. The following output is displayed:

nc14uf010.eps
For the sake of clarity, the values of the horizontal scale as well as the width and position of the histogram bars have been changed
In the previous dialog boxes, instead of writing all the values ...

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