Measurement
What is measurement?
Measurement has been defined as the "process of linking abstract concepts to empirical indicants."1 That is, in this case we are attempting to measure a physiological phenomenon, blood pressure, and obtain a number that represents what is going on in the underlying process.
How do we know that the measurement is correct?
Ms. Jones' blood pressure as measured today in your office is made up of the actual physiological pressure plus any error in measurement which might have been made. In order to get as close to the "true" blood pressure we must eliminate as much of the error as possible. A "true score" could be obtained if we took Ms. Jones BP an "infinite" number of times. Of course, this is not feasible.
