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

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21.5 Plastic (2nd Part)

In addition to the values of the length being controlled, every hour, together with the extraction of the subgroup, measures of the pressure, viscosity, and temperature of injection are also taken. This information is contained in file PLASTIC_2.MTW.
The questions raised by the improvement team are the following: Do these data allow the identification of any special cause that may affect the variable length? Under which conditions of pressure, viscosity and temperature does it seem to be reasonable to inject? Is it possible to make the process capable?

The content of this file (PLASTIC_2.MTW) has the following appearance:

nc21uf018.eps

It is helpful for the analysis to have the mean and range of each subgroup in the same worksheet. To obtain this, open worksheet PLASTIC_1.MTW and do the following.

Calc > Make Patterned Data > Simple Set of Numbers

nc21uf018.eps

Stat > Basic Statistics > Store Descriptive Statistics

nc21uf019.eps

Hence, worksheet PLASTIC_1.MTW now looks as follows:

nc21uf020.eps

The last thing to do is to copy columns C6 and C7 and add them to the worksheet named Plastic_2 (just by ...

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