intro to statistics basic

Question

Persons taking a 30-hour review course to prepare for a standardized exam average a score of 620 on that exam. Persons taking a 70-hour review course average a score of 746. Find a linear equation in slope-intercept form which fits this data.

Answer 1

Let x1=30, y1=620, x2=70, and y2=746

The slope is (y2-y1)/(x2-x1) = (746-620)/(70-30) = 126/40 = 3.15

For slope-intercept, solve the equation

y-y1 = slope(x-x1)

y-620 = 3.15(x-30) = 3.15x - 94.5

Add 620 to both sides to get y = 3.15x + 525.5. This is the equation you want.

As a check, let x=70.

Then y = 3.15*70 + 525.5 = 220.5 + 525.5 = 746, so it checks