| One of the most important aspects of any quality | | | | procedures open the door to another difference in |
| system is the control of monitoring and | | | | operators, "interpretation" of the requirements or |
| measurement processes. The systematic and random | | | | methodology. |
| errors that can influence test results or process | | | | Laboratory Environment |
| monitoring results can be from a variety of sources. | | | | Some samples and equipment may be susceptible to |
| It is important to identify the cause and effect | | | | temperature, humidity, atmospheric pressure, and |
| relationships that can create the variability observed | | | | other environmental factors. Because these cannot |
| in test results. Generally, these sources can be | | | | be controlled perfectly within or between labs, they |
| summarized into the following categories: | | | | provide some contribution to the variation of test |
| Equipment | | | | results. |
| The equipment, whether it is a sophisticated | | | | Samples |
| automated electronic analyzer or glassware, has been | | | | Any non-uniformity of the sample can cause |
| manufactured to certain tolerances. The variability | | | | additional differences in test results. When conducting |
| inherent to the equipment specifications will be | | | | studies to determine testing variability, special effort |
| reflected in the test results. Component wear, failure, | | | | must be made to obtain test samples that are as |
| or inadequate maintenance will increase the | | | | uniform or similar as possible. |
| inconsistencies in test results. Any inconsistencies in | | | | Time |
| calibration verification and/or recalibration will also | | | | All of the previously mentioned sources of variation |
| affect the consistency of the results obtained from | | | | can themselves change with time. In measurement |
| the equipment. | | | | studies, efforts are usually made to keep the time |
| People | | | | span as short as practical. |
| People are almost always a contributor to some of | | | | When taken together these many sources can cause |
| these differences in results simply because none of | | | | significant issues with the repeatability and |
| us are exactly alike. We differ in dexterity, reaction | | | | reproducibility of a measurement process. It is |
| times, color sensitivity, and other ways. Even the | | | | essential that steps be taken to minimize the |
| same operators can perform differently at different | | | | differences in test results obtained within a given |
| times due to different degrees of mental and | | | | laboratory or Quality Control area. Working to reduce |
| physical alertness. Some operator differences are | | | | the effects of any or all of these sources can |
| practically unavoidable. Of course, some tests are | | | | improve the consistency of your results and build |
| more sensitive to the effects of operator | | | | confidence in your quality system. |
| differences. Incomplete or confusing test methods or | | | | |