Principles of Food Sanitation

136 PRINCIPLES OFFOODSANITATION

with all data points lying within the bound-
aries of the control limits and an equal num-
ber of points above and below the center line.

Attribute Control Charts

Attribute control charts differ from meas-
urements charts in that one is interested in

an acceptable or unacceptable classification

of products. The following charts are com-

monly used for attribute testing:

1.pcharts

2.npcharts

3.ccharts

4.ucharts

3

1234

Sample Number

5678

3.5

4

4.5

5

5.5

6

pH

UCL = 4.79

LCL = 4.10

Figure 8–7Xchart for pH measurements.

0.00

12345678

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

pH

UCL = 1.24

LCL = 0

Sample Number

Figure 8–8Rchart for pH measurements.