Besides the types of variables we have discussed in lesson 4, Variables are also classified according to the role they play in a study and also based on the mathematical values that they take in a continuum. Thus we have experimental classification and mathematical classification. This lesson discusses the mathematical classification where variables are either classified as discrete or continuous. Discrete variables can only take whole numbers while continuous variables can take any value within a continuum, they do not have a minimum sized value. These two categories leads us to scales of measurement or in some books they are referred to as levels of measurement. Discrete variables are measured at nominal and ordinal scale or level. In this scale, numbers carry qualitative value meaning they are non-numeric. Continuous variables are measured at interval and ratio scale where numbers carry a quantitative value. Welcome to this lesson as we explore those classification and scales of measurement.