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

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12.4 Arrow

An arrow shaped plastic pieces are made with two injection moulding machines: A and B. Each machine has its own mould with 4 cavities, as shown in the following figure:
Data is available on ARROW.MTW file:
Column Content
C1 C2 C3 C4 C5 Defects found in the parts produced by machine A As C1, but for machine B Tensile strength of parts made in 15 injections with machine A (15×4 = 60 data) As C3 for machine B Cavity to which data from columns C3 and C4 belong.
The questions we pose are:
1. Looking at the distribution of defects in each machine, should the improvement measures be equally prioritized for both machines?
2. As for the tensile strength, is there a difference between machines? And between cavities?
1. Let's see what is the distribution of defects in each machine by: Stat > Quality Tools > Pareto Chart Doing the same for the machine B: Assuming that the data are representative of both machines, it would be appropriate to focus on the problem of deformation in machine A and scratches in machine B.
2. First of all, a graphical analysis ...

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