Rizal Works

SCALES OF MEASUREMENT

There are four scales (or levels) at which we measure. The lowest level is the nominal scale. This may be thought of as the “naming” level. For example, when we ask subjects to name their marital status, they will respond with words—not numbers—that describe their status such as “mar-ried,” “single,” “divorced,” etc. Notice that nomi-nal data do not put subjects in any particular order. There is no logical basis for saying that one category such as “single” is higher or lower than any other.

The next level is ordinal. At this level we put subjects in order from high to low. For in-stance, an employer might rank order applicants for a job on their professional appearance. Tradi-tionally, we give a rank of 1 to the subject who is highest, 2 to the next highest, and so on. It is im-portant to note that ranks do not tell us by how much subjects differ. If we are told that Janet has a rank of 1 and Frank has a rank of 2, we do not know if Janet’s appearance is greatly superior to Frank’s or only slightly superior. To measure the amount of difference among subjects, we use the next levels of measurement.

Measurements at the interval and ratio lev-els have equal distances among the scores they yield. For example, when we say that Jill weighs 120 pounds and Sally weighs 130 pounds, we know by how much the two subjects differ. Also, note that a 10 pound difference represents the same amount regardless of where we are on the scale. For instance, the difference between 120 and 130 pounds is the same as the difference be-tween 220 and 230 pounds.

The ratio scale is at a higher level than the in-terval scale because the ratio has an absolute zero point that we know how to measure. Thus, weight is an example of the ratio scale because it has an absolute zero that we can measure.

The interval scale, while having equal inter-vals like the ratio scale, does not have an absolute zero. The most common examples of interval scales are scores obtained using...