INE 326 Statistical Quality Control – Spring 2012 (HW#3
Solution
)
CH 6
6.2.
The net weight (in oz) of a dry bleach product is to be monitored by and R control charts using a
sample size of n=5. Data for 20 preliminary samples are shown in Table 6E.2.
Table 6E.2
(a)
Set up and R control charts using these data. Does the process exhibit statistical control?
(b)
Estimate the process mean and standard deviation.
(c)
Does fill weight seem to follow a normal distribution?
(d)
If the specifications are at 16.2
±
0.5, what conclusions would you draw about process
capability?
(e)
What fraction of containers produced by this process is likely to be below the lower
specification limit of 15.7 oz?

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Sol)
(a)
The process is in statistical control with no out-of-control signals, runs, trends, or cycles.
(b)
2
5;
16.268;
0.475;
/
0.204
x
n
x
R
R
d
σ
=
=
=
(c)
Shapiro-Wilk Test
Test result
W = 0.96475293
Fail to reject H0(=Normal distribution)