You are investigating the complaints and have measured the diameter of 120 pins from inventory, 40 from each of the three suppliers, thinking that variation in pin diameters may be related to the loose pins. In order to have a good fit, the target value for the pin diameter was specified to be 10mm, with an upper specification limit of 10.2mm, and lower limit of 9.8mm. A table of the data is provided in the next worksheet. The data is listed in the order that the parts were taken from inventory, but the original production sequence is unknown.

a) Calculate the mean and standard deviation for parts from each supplier. Display your results to 5 decimal places.

b) Why would run charts (or control charts) be less appropriate for graphing this data?

c) Which type of graphical chart would best help you to visually understand the distribution of pin diameters? Construct that chart(s).

d) Evaluate the process capability of each supplier (in terms of process capability indexes, etc.). Display any results to 4 decimal places.

e) What are your conclusions and recommendations?

Supplier	Diameter
A	9.95
A	10.04
A	9.96
A	10.00
A	9.88
A	10.03
A	10.01
A	9.97
A	9.96
A	9.91
B	10.12
B	9.83
B	10.17
B	9.86
B	10.14
B	10.07
B	9.88
B	10.13
B	9.84
B	10.19
C	9.90
C	9.88
C	9.91
C	9.97
C	9.86
C	9.81
C	9.98
C	9.91
C	9.84
C	9.87
A	9.98
A	9.99
A	9.97
A	9.91
A	10.01
A	10.04
A	9.96
A	10.02
A	9.98
A	10.08
B	9.86
B	9.80
B	10.13
B	9.94
B	9.67
B	10.16
B	10.10
B	9.85
B	9.64
B	10.13
C	9.87
C	9.83
C	9.96
C	9.88
C	9.94
C	10.03
C	9.86
C	9.93
C	9.82
C	9.93
A	9.97
A	10.04
A	10.13
A	10.01
A	10.03
A	9.96
A	10.14
A	10.02
A	10.00
A	9.94
B	10.12
B	10.04
B	9.85
B	10.15
B	10.07
B	9.78
B	10.11
B	9.92
B	10.12
B	9.86
C	9.86
C	9.80
C	9.97
C	9.84
C	9.87
C	10.07
C	9.81
C	9.85
C	9.94
C	9.81
A	10.05
A	9.99
A	10.06
A	10.01
A	9.96
A	10.01
A	9.93
A	10.04
A	10.14
A	9.95
B	9.82
B	9.95
B	9.88
B	10.08
B	10.14
B	9.68
B	9.91
B	9.89
B	10.08
B	9.81
C	9.84
C	9.85
C	9.82
C	9.95
C	9.88
C	9.87
C	9.92
C	9.81
C	10.02
C	9.83