In The Slope of a Line, you learned that the slope, or *m*, of a line describes how rapidly or slowly change is occurring.

Linear Functions have 4 types of slopes: positive, negative, zero, and undefined.

### Positive Slope = Positive Correlation

A positive slope demonstrates a positive correlation between the following:

*x*and*y*- input and output
- independent variable and dependent variable
- cause and effect

**Positive correlation** occurs when each variable in the function moves in the same direction. Look at the linear function in the picture, Positive slope, *m* > 0. As the values of *x* **increase**, the values of *y* **increase**. Moving from left to right, trace the line with your finger. Notice that the line **increases**.

Next, moving from right to left, trace the line with your finger. As the values of *x* **decrease**, the values of *y* **decrease**. Notice how the line **decreases**.

### Positive Slope in the Real World

Samantha is planning a family reunion. The more people who attend (**input**), the more chairs she orders (**output**).

James is visiting the Bahamas. The less time that he spends snorkeling (**input**), the fewer tropical fish he spies (**output**).

### Calculating Positive Slope

To calculate a positive slope, where *m*>0, see the examples from How to Find the Slope of a Line With a Graph and Calculate Slope With a Formula.