ASTM D4697-95(2001)

1.1 This guide is intended to assist laboratories in maintaining precision and controlling bias in testing. It includes statistical procedures for detecting lack of control, changes in calibration constants, and in operator technique. Suggestions are given for the correction of some out of control situations.

1.2 This guide includes the following topics:

1.3 This standard does not give all of the details for preparing statistical quality control charts or the statistical tests used to interpret them, but such information may be found easily in a number of publications.

Following this guide will aid the user in maintaining control of both the bias and the precision of any test method.

4.1.1 It is necessary to control bias so that, if a change in level of an unknown material under test occurs, the user can be confident that the change was not due to the execution of the test method.

4.1.2 It is also necessary to control precision so that the established confidence limits and critical differences will be maintained.

Should the use of the test method be out of control, this guide will detect it, and may give an indication of where the problem lies.