. The process is in control. The table below computes the proportion of defectives for each day, as well as p bar and the control limits. The data are then charted. (The line containing triangles is the UCL; p bar is the line containing squares; the LCL is zero.) However, the term "in control" does not necessarily mean that the number (or proportion) of defects is acceptable, but only that it is random and has a stable average. Because it is not acceptable here, we may benefit from a more detailed look.

Here we are really dealing with three processes, so it makes sense to analyze each one.

Day

Defective Bills

Proportion Defective (p)

1

4

0.20

2

2

0.10

3

0

4

5

0.25

5

2

0.10

6

0

7

1

0.05

8

0

9

5

0.25

10

1

0.05

11

4

0.20

12

2

0.10

13

0

14

5

0.25

15

3

0.15

16

0

17

5

0.25

18

2

0.10

19

1

0.05

20

0