The slope of a line tells you the rate of change—how much $y$ changes when $x$ increases by 1. Think about what happens to the predicted test score when study time increases by 1 hour.

Since $x$ is study time (hours) and $\hat{y}$ is predicted test score (points), the slope should describe how many points the score changes per hour of study. Look for an answer that matches this pattern.

In Desmos, type y = 66 + 2.4x to see the line. Notice that it slopes upward, confirming a positive relationship.

Click on the line at $x = 0$ (you will see $y = 66$) and at $x = 1$ (you will see $y = 68.4$). The difference $68.4 - 66 = 2.4$ confirms the slope.

The equation $\hat{y} = 66 + 2.4x$ is in slope-intercept form $\hat{y} = a + bx$, where:

• $a = 66$ is the $y$-intercept (the predicted value when $x = 0$)
• $b = 2.4$ is the slope (the rate of change)

The slope $b = 2.4$ tells us that for each 1-unit increase in $x$ (study time), the predicted value of $y$ (test score) increases by 2.4 units.

In context: For each additional hour of study time, the predicted test score increases by 2.4 points.

The answer that correctly describes the slope is: "For each additional hour of study time, the predicted test score increases by 2.4 points."

This matches the definition of slope as the change in $y$ per unit change in $x$.