Variables refer to quantifiable characteristics of data and can be expressed numerically. Examples of variable are wages, age, height, weight, marks, distance, etc. As you know, all these variables can be expressed in quantitative terms. In this form of classification, the data is shown shown in the form of a frequency distribution. A frequency distribution is a tabular presentation that generally organises data into classes, and shows the number of observations (frequencies) falling into each of these classes. Based on the number of variables used, there are three categories of frequency distribution :

1) uni-variate frequency distribution, 2) bi-variate frequency distribution, and 3). multivariate frequency distribution.

In this unit we will discuss uni-variate analysis and bi-variate analysis only.

**1) Uni-variate Frequency Distribution:** The frequency distribution with one variable is called a uni-variate frequency distribution. For example, the students in a class may be classified on the basis of marks obained by them.

**2) Bi-variate Frequency Distribution:** The frequency distribution with two variable is called bi-variate frequency distribution. If a frequency distribution shows two variables i.e., marks in statistics and age, it is known as bi-variate frequency distribution.