That is the data are expressed in terms of categories. The data cannot be arranged in any order with respect to one another. Ordinal level data are also categorical but the categories can be ordered with respect to one another. The ordinal level of measurement involves data that may be arranged in some order, but differences in data values either cannot be determined or are not important. In this example lower middle class denotes a smaller income than in the other two classes but the amount of the difference is arbitrary.
Interval data differ from ratio data inasmuch as there is no inherent absolute zero point.
Examples of ratio data include age, weight, height, or distance. If you still are not certain how to start this selection process you should look at the grid selection model provided by the Virtual Statistical Assistant. The VSA was constructed by students in the Department of Communication Studies . Please send feedback and comments to VSA staff .