Operational definitions

A specific statement about how an event or behavior will be measured to represent the concept under study. See also indicator and research methods. http://www.utexas.edu/academic/diia/assessment/iar/glossary.php

Notes from  Research Methods class (Roy Maxion):

1. Identify the characteristic of interest.
2. Get a dictionary definition.
3. Select the measuring instrument.
4. Describe the test method.
5. State the decision criteria.
6. Document the operational definition.
7. Test the operational definition.

Operational definition – example (attribute)
Characteristic of interest:
– Number of black spots per radiator grill.
Measuring instrument:
– The observation will be performed with the naked eye (or with corrective lenses if normally worn), under the light available in the work station (in 100% working order, i.e., no burned-out bulbs).
Method of test:
– The number of black spots per radiator grill will be counted by taking samples at the work station. The sample should be studied at a distance of 18 inches (roughly half an arm’s length) from the eye. Only the top surface of the grill is to be examined.
Decision criteria:
– Wipe the top surface of the grill with the palm of your hand and look for any black specks embedded in the plastic. Any observed black speck of any size counts as a black spot.
Test the definition:
– Try it out with N observers; see if there is agreement among them.

Operational definition – example (variable)
Characteristic of interest:
-Diameter of 48-inch rod – acceptability for delivery.
Measuring instrument:
-Micrometer
Method of test:
– The sample size is 3. Measure 3 rods every hour. When the grinder releases the rod, take one measurement each at (a) 8″ down, (b) 24″ down, and (c) 40″ down from the notched end. Tighten the micrometer as much as possible. Record to 4 decimal points. If the fifth number to the right of the decimal point is 5 or higher, round up the fourth number by one.
Decision criteria:
– (A) If the three measures do not differ by more than 0.0001, then the rod passes the invariance test. (B) if the three measures also are within 0.0005 of ½ inch, then the rod passes the diameter test.
Test the definition:
– Test the procedure on calibrated rods; use several people; validate with inter-rater reliability test.

Question: what is the difference between an attribute and a variable?  Is one “absolute” and the other a sample?