Identify the characteristic of interest.
Identify the characteristic to be measured or the defect type of concern.
Select the measuring instrument.
The measuring instrument is usually either a physical piece of measuring equipment such as a micrometer, weighing scale, or clock; or alternatively, a visual check. Whenever a visual check is used, it is necessary to state whether normal eyesight is to be used or a visual aid such as a magnifying glass. In the example, normal eyesight is sufficient. On some occasions, it may also be necessary to state the distance the observer should be from the item being checked. In general, the closer the observer, the more detail will be seen. In the example, a clear visual indication is given of acceptable and unacceptable, so the observer needs to be in a position where the decision can be made. When completing a visual check, the type of lighting may also need to be specified. Certain colors and types of light can make defects more apparent.
Describe the test method.
The test method is the actual procedure used for taking the measurement. When measuring time, the start and finish points of the test need to be specified. When taking any measurement, the degree of accuracy also needs to be stated. For instance, it is important to know whether time will be measured in hours, minutes, or seconds.
State the decision criteria.
The decision criteria represents the conclusion of the test. Does the problem exist? Is the item correct? Whenever a visual check is used, a clear definition of acceptable versus unacceptable is essential. Physical examples or photographs of acceptable and unacceptable, together with written support, are the best definitions.
Document the operational definition.
It is important that the operational definition is documented and standardized. Definitions should be included in training materials and job procedure sheets. The results of steps 1 through 4 should be included in one document. The operational definition and the appropriate standards should be kept at the work station.
Test the operational definition.
It is essential to test the operational definition before implementation. Input from those that are actually going to complete the tests is particularly important. The operational definition should make the task clear and easy to perform. The best way to test an operational definition is to ask different people to complete the test on several items by following the operational definition. Watch how they perform the test. Are they completing the test as expected? Are the results consistent? Are the results correct?
