Page 38 - Quality control of pharmaceuticals (07-PA 704)

The second part of a quality control program is a control chart. This
is a graph that uses the results obtained with a control material to
follow the performance of an analytical method over time.

Purpose of control charts
The purpose of control charts is to distinguish between natural
variations and variations due to assignable causes.
Natural variations affect almost every production process and are to be
expected, even when the process is in statistical control.They are
random and uncontrollable.
Assignable variations are not random and can be controlled.
The objective of Control charts is to provide a statistical signal when
assignable causes of variation are present.
This chart can indicate when a change has occurred in the systematic
or random errors of a method by comparing the result for the
control material to the range of results that would normally be
expected for the same material.
If a new result is outside of this range, the analytical method should
be examined to ensure it is working properly before any other
samples are tested.

Preparing and Using Control Charts
Lets now look closely at one of the key components of a quality-control

program, the control chart.