# DETERMINING THE ASSOCIATION BETWEEN TWO VARIABLES

## About "Determining the association between two variables"

Determining the association between two variables :

Association describes how sets of data are related. A positive association means that both data sets increase together. A negative association means that as one data set increases, the other decreases. No association means that there is no relationship between the two data sets.

Data that show a positive or negative association and lie basically along a line exhibit a linear association. Data that show a positive or negative association but do not lie basically along a line exhibit a nonlinear association.

## Determining the association between two variables - Examples

Example 1 :

David asked 20 people if they can buy a new product that he developed at each of several prices. The scatter plot shows how many of the 20 people said “yes” at a given price. Describe the association between price and the number of buyers.

Solution :

When price gets increased, the number of buyers gets    decreased. So, there is a negative association. Because the data points do not lie along a line, the association is non-linear.

Example 2 :

A survey made among students in a district and the scatter plot shows the level of reading and height for 16 students in the district. Describe the association and give a possible reason for it.

Solution :

Positive and basically linear :

The students who are taller read at a higher level.

Example 3 :

Jack recorded his height at different ages. The scatter plot shows the his height at different ages. Describe the association between age and height and give a possible reason for it.

Positive and basically linear :

When Jack gets older, his height gets increased. But if the data continued for increasing age, we can see that Jack’s height will stop increasing.

## Reflect

1. Based on the association shown in the scatter plot in example 1, what might happen if David increased the price to \$14 ?

It is likely that no one would buy the product.

2. In example 3, if the data continued for increasing age, we can see that Jack’s height will stop increasing. why ?

Naturally, height of human being will stop increasing at a particular age. Even if age gets increased, after a particular age, height will not increase.

After having gone through the stuff given above, we hope that the students would have understood, how to determine the association between two variables

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