Measurement is the process of systematic observation and assignment of numbers to phenomena according to rules. The word process can be defined as a set of progressive, interdependent steps. In other words, when we measure something, there is a series of steps that we must go through.
In measurement, numbers are assigned to represent “things”. Its important if our measurement is to be of any value that the numbers and the things are isomorphic. Isomorphism means identity or similarity of form.
Nominal measurement is a simple classification. Numbers vs. Sex(male/female). It merely indicates the things that are different from one another.
Ordinal or rank-order measurement assigns numbers to things in such a way as to reflect relationships among the things. It indicates the direction of the difference in some meaningful way.
Interval measurement has all of the characteristics of ordinal measurement and one crucial addition. Interval measurement identifies the distance between any two things that are measured.
Ratio scale has all of the characteristic of an interval scale, but in addition is has a true zero point as its origin. Zero could mean different things on the two different measures. In ratio measures, zero has an absolute value of its own. Blah blah blah