It has properties of the ordinal level of measurement and the differences in the values of the variable have meaning. A value of zero in the interval level of measurement does not mean the absence of the quantity. Arithmetic operations such as addition and subtraction can be performed on values of the variable is called interval. While nominal the values of the variables name, label or categorize. In addition, the naming scheme does not allow values of the variables to be arranged in a ranked or specific, order.