<P> Nominal scales were often called qualitative scales, and measurements made on qualitative scales were called qualitative data . However, the rise of qualitative research has made this usage confusing . The numbers in nominal measurement are assigned as labels and have no specific numerical value or meaning . No form of mathematical computation (+, -, x etc .) may be performed on nominal measures . The nominal level is the lowest measurement level used from a statistical point of view . </P> <P> Equality and other operations that can be defined in terms of equality, such as inequality and set membership, are the only non-trivial operations that generically apply to objects of the nominal type . </P> <P> The mode, i.e. the most common item, is allowed as the measure of central tendency for the nominal type . On the other hand, the median, i.e. the middle - ranked item, makes no sense for the nominal type of data since ranking is meaningless for the nominal type . </P> <P> The ordinal type allows for rank order (1st, 2nd, 3rd, etc .) by which data can be sorted, but still does not allow for relative degree of difference between them . Examples include, on one hand, dichotomous data with dichotomous (or dichotomized) values such as' 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 the other hand, non-dichotomous data consisting of a spectrum of values, such as' completely agree',' mostly agree',' mostly disagree',' completely disagree' when measuring opinion . </P>

Scale of measurement which has no order distance and unique origin is known as