Ordinal scale Level of measurement

the ordinal type allows rank order (1st, 2nd, 3rd, etc.) data can sorted, still not allow relative degree of difference between them. examples include, on 1 hand, dichotomous data dichotomous (or dichotomized) values such sick vs. healthy when measuring health, guilty vs. not-guilty when making judgments in courts, wrong/false vs. right/true when measuring truth value, and, on other hand, non-dichotomous data consisting of spectrum of values, such agree , agree , disagree , disagree when measuring opinion.

central tendency

the median, i.e. middle-ranked, item allowed measure of central tendency; however, mean (or average) measure of central tendency not allowed. mode allowed.

in 1946, stevens observed psychological measurement, such measurement of opinions, operates on ordinal scales; means , standard deviations have no validity, can used ideas how improve operationalization of variables used in questionnaires. psychological data collected psychometric instruments , tests, measuring cognitive , other abilities, ordinal, although theoreticians have argued can treated interval or ratio scales. however, there little prima facie evidence suggest such attributes more ordinal (cliff, 1996; cliff & keats, 2003; michell, 2008). in particular, iq scores reflect ordinal scale, in scores meaningful comparison only. there no absolute zero, , 10-point difference may carry different meanings @ different points of scale.