An internal quality control sample of blood, used for checking the accuracy of blood alcohol determinations, contains 80.0 mg 100 ml-1 of ethanol. Successive daily measurements of the alcohol level in the sample were made using four replicates. The precision (process capability) of the method was known to be 0.6 mg 100 ml-1. The following results were obtained:
|
Day
|
Concentration (mg 100 MI-')
|
|
1
|
79.8
|
|
2
|
80.2
|
|
3
|
79.4
|
|
4
|
80.3
|
|
5
|
80.4
|
|
6
|
80.1
|
|
7
|
80.4
|
|
8
|
80.2
|
|
9
|
80.0
|
|
10
|
79.9
|
|
11
|
79.7
|
|
12
|
79.6
|
|
13
|
79.5
|
|
14
|
79.3
|
|
15
|
79.2
|
|
16
|
79.3
|
|
17
|
79.0
|
|
18
|
79.1
|
|
19
|
79.3
|
|
20
|
79.1
|
Plot the Shewhart chart for the mean, and the cusum chart, for these results, and comment on the outcomes.