Correlation, Coefficient of Correlation, Types and Uses

by Yuvi - April 10, 2022

Correlation

Correlation is a measure of relationship. It is a statistical procedure that helps us to examine the relationship of one variable with another. When the increase or decrease of one variable corresponds to the increase or decrease of another, the 2 variables are said to be correlated. The converse is also true.

Coefficient of correlation

A Coefficient of correlation is a single number that tells us to what extent two things are related, to what extent variations in one go with the variations in another.

Types of correlation

1. Positive – When 2 variables are directly proportional. i.e. increase or decrease in one leads to increase or decrease in the other respectively.

• • Eg. Increase in demand for milk leads to increase in supply.
  • Eg. Decrease in rainfall leads to decrease in water supply.
  • Eg. 400m race will take more time to finish than 100m race.
  • Eg. Increase in temperature leads to increase in sweating.

1. Negative – When 2 variables are indirectly proportional. i.e. increase or decrease in one leads decrease or increase in the other respectively.

• • Eg. When value education increases, crime decreases.
  • Eg. Population increases, resources reduce.
  • Eg. Speed decreases, time taken to reach a place increases.
  • Eg. Decrease in number of students increases time for individual attention.
  • Eg. Altitude increases, oxygen level decreases.

1. Zero – When there is no relation between 2 variables or no effect of one variable on another.

• • Eg. Cooking and writing skills have no relation.
  • Eg. Intelligence and number of hair.
  • Eg. History and music skills.

Uses of correlation

• While preparing a test.
• To determine validity of a test.
• To determine reliability of a test.
• To compare objectivity in scoring between two examiners.
• To credit or discredit validity of arguments.
• To compare and decide relationship between 2 variables.
• In guidance and counselling.