It is a system of assigning number symbols to in order to label the events. For example when there is assignment o numbers to basket ballplayers for the purpose of their identification. The track of people, objects and events could be conveniently kept with the help of nominal scale there is nothing much that could be done with numbers its like the researcher would not be able to usefully average the numbers writing on the back of the a group of football players and finally come up with a meaningful value.
The comparison between one group and the other could also not be made. When a nominal scale is made use of the counting of numbers in each group is the only possible arithmetic operation to be made use of. According to precedence, the researcher is constrained to use mode as the measure of central tendency. Generally, there is no used measure of dispersion for nominal scales.
One test of significance that could be used is the Chi-square test of statistical significance for the measures of correlation and therefore the contingency coefficient could be worked out.