1. Meaning of Correlation
Correlation describes how two quantities change together. If one quantity changes and another quantity also changes in a related way, we say that the two are correlated.
Correlation helps understand whether an increase or decrease in one variable is linked with an increase or decrease in another.
For example, as temperature increases, the sale of cold drinks often increases. This shows a positive relationship between the two.
2. Types of Correlation
The direction of the relationship between two variables helps classify correlation. It tells whether the variables move in the same direction, opposite directions, or show no relation at all.
2.1. Positive Correlation
Two variables show positive correlation when they increase or decrease together. In simple terms: more of one means more of the other. For example, height and weight often rise together.
2.2. Negative Correlation
2.3. Zero Correlation
If two variables do not influence each other at all, they show zero correlation. For example, shoe size and marks scored have no meaningful connection.
3. Direction and Strength of Correlation
Correlation not only shows direction but also indicates how strong or weak the relationship is. Strength tells how closely the two variables move together.
3.1. Strong and Weak Correlation
If the points or values follow a clear pattern—either rising or falling—the correlation is strong. When the pattern is loose, the correlation is weak.
Examples:
- Strong positive: As study time increases, marks tend to increase.
- Weak positive: As temperature rises, ice-cream sales rise, but with some variation.
- Strong negative: More exercise time often means less body fat.
- Weak negative: As age increases, outdoor activity may decrease slightly.
4. Real-Life Examples of Correlation
Correlation appears naturally in many real situations. Some common examples include:
- Height and weight
- Hours of practice and performance level
- Temperature and electricity usage
- Fuel in a vehicle and distance it can travel
These examples make it easier to understand how two quantities may be related in predictable ways.