we defined variables as characteristics or conditions that change have different values for different individuals. Usually researchers are interested in how variables are affected by different conditions or how variables differ from one group of individuals to another. For example, a clinician may be interested in how depression scores change in
response to therapy, or a teacher may want to know how much difference there is in the reading scores for third-grade children versus fourth-grade children To evaluate differences or changes in variables, it is essential that we are able to measure them. Thus, the next step in the research process (Step 3) is determining a method for defining and measuring the variables
that being studied.