In a linear relationship, two variables or quantities are proportionate to one another. As one variable changes, there is a constant rate of change in another variable. In a graphic representation, a linear relationship is a straight line that passes through data points based on the slope and rate of change.
Positive linear relationships involve the two variables moving in the same direction. Both variables either increase or decrease with each unit change. In a negative linear relationship, an increase or decrease in one variable correlates to a decrease or increase in the other variable. The variables move in opposition of one another.