How to Calculate Bivariate Frequency Distribution?

1. The two variables involved in a bivariate set of data may be discrete, continuous, or one discrete and one continuous. One of these is represented horizontally, while the other is shown vertically.

2. Considering the nature of the variables involved and the magnitude of values in the data, an appropriate decision is taken regarding the individual values of the variable, how many classes, and what width is to be taken. In this way, a bivariate table is created.

3. After this, each pair of the values is considered and entered in the appropriate cell in the table by means of a tally bar.

4. Once all pairs are considered, and entries are made, the tally bars in each cell are counted, and frequencies for each of the cells are determined.

5. Finally, the row and column totals are obtained to get marginal frequencies.

Example 1:

Prepare a bivariate frequency distribution for the following data, taking class intervals for X as 25-35, 35-45, 45-55, etc., and for Y as 105-120, 120-135, etc. where X denotes the age in years and Y denotes blood pressure for a group of 20 people. 

The required data is: (45, 141); (26, 130); (62, 150); (28, 114); (55, 138); (36, 120); (48, 142); (40, 139); (28, 105); (32, 135); (31, 153); (37, 151); (59, 149); (50, 151); (48, 121); (47, 126); (33, 131); (42, 154); (49, 151); (34, 118).

Solution:

Given, X = Age in years, Y = Blood Pressure. 

Bivariate Frequency Distribution is to be prepared by taking class intervals for X as 25-35, 35-45, 45-55, etc., and for Y as 105-120, 120-135, etc.

Bivariate Frequency Distribution

Marginal Frequency Distribution of X:

Marginal Frequency Distribution of Y: