Design of Experiments and Statistical Process Control - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 233

Sample Number Result

1 48

2 51.3

3 49.5

4 52.3

5 50.6

6 47.3

7 50.2

8 51.1

9 50

10 50.7

11 49.6

12 49.7

13 48.2

14 50.3

15 46.5

16 49.9

17 53.3

18 52.4

19 48.5

20 52.8

Figure 13.8 Table of Process Results

We can graph the results (Figure 13.9):
It is still not clear. If we calculate the average and the standard deviation
and assume a normal distribution, we can say that there is a 99.7% likelihood
that a number will fall within three standard deviations. The average is 50.1%
and the standard deviation is 1.8. This tells us that if it is a normal distribu-
tion, there is a 99.7% probability that a random point will fall between 44.7%
(50.1 - 3(1.8)) and 55.5% (50.1

3(1.8)). Replotting with lines for three
standard deviations, our plot looks like this (Figure 13.10).

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