sizes from unequal inspection samples. The
number of equivalent common basic lot
sizes (k) can be calculated as:
size of common lotsize of sample lot
k=
Theustatistic can be determined from c,
the number of defects of a sample lot, and
thekvalue defined in the above equation.
u=kc
From these values, the upper and lower
control limits for the uchart can be defined as:
UCL=+u (^3) ku
LCL=-u (^3) ku
In addition to charting, a manufacturer
may introduce other statistical analyses, such
as modeling, variable correlations, regres-
sion, analysis of variance, and forecasting to
the production area. These techniques pro-
vide additional statistical methods for exam-
ining processes in order to ensure maximum
production efficiency.
Explanation and Definition of Statistical
Quality Control Program Standards
The following terms apply to maintenance
of standards:
●Standard: The level or amount of a spe-
cific attribute desired in the product.
●Quality attribute: A specific factor or
characteristic of the food product that
determines a proportionate part of
the acceptability of the product. Attrib-
utes are measured by a predetermined
method, and the results are compared
against an established standard and
lower and upper control limits to deter-
mine if the product attribute is at the
desired level in the food product.
●Retained product:A product that is not
to be used in production or sold until
corrective action has been taken to meet
the established standards. Retained
products should not be released for pro-
duction or sales use until the problem is
corrected.
Rating Scales
Two rating scales have been devised for
evaluation of attributes:
1.Exact measurement:For attributes that
can be measured in precise units (bacte-
rial load, percentage, parts per million,
etc.).
2.Subjective evaluation: Used when no
exact method of measurement has been
developed. The evaluation must be con-
ducted through sensory judgment
(taste, feel, sight, smell). This is usually
described numerically. Two scales have
been developed for evaluating accept-
ability:
Scale 1 Scale 2
7—Excellent 4 —Extreme
6—Very good 3—Moderate
5—Good 2—Slight
4 —Average 1—None
3—Fair
2—Poor
1—Very poor
The number of samples to conduct at any
point during production to evaluate the san-
itation operation also depends on the varia-
tions of analysis of the samples. A minimum
of three to five samples of approximately
2 kg each should be selected and pooled
from each lot of incoming raw material.
After a sufficient number of samples have
been analyzed, control charts can be con-
structed for each raw material.
Sampling of the finished product should
be conducted at a special step in the produc-
tion sequence, such as at the time of packag-
ing. Sampling at this stage does not need to
be done on individual products for inspec-