Measurement is assigning numbers to variables according to rules (Kerlinger, 1986).

1.Nominal Scales(Categorical): Variables are nominal. Numbers are assigned merely for distinction. Ex. Gender, Race

2.Ordinal Scales: Variables have rank values and can be ordered . There’s no meaningful zero. Grades as AA, BB or Level of Education such as High School, Undergraduate and so on.

3.Interval Scales: Ex. People with age 18 - 25

4.Ratio Scales: Numbers assigned to variables have equal intervals and a zero that has a meaning. Ex. Annual Income, Class Attendance.

Sowell, Evelyn J.(2000). Educational Research: An Integrative Introduction. United States: McGraw-Hill.