Math Snap
PROBLEM
A researcher wishes to examine the relationship between years of schooling completed and the number of pregnancies in young women. Her research discovers a linear relationship, and the least squares line is: where x is the number of years of schooling completed and y is the number of pregnancies. The slope of the regression line can be interpreted in the following way:
When amount of schooling increases by one year, the number of pregnancies tends to decrease by 3 .
When amount of schooling increases by one year, the number of pregnancies tends to increase by 3 .
When amount of schooling increases by one year, the number of pregnancies tends to increase by 4 .
When amount of schooling increases by one year, the number of pregnancies tends to decrease by 4 .
STEP 1
What is this asking?
How does the number of pregnancies change when years of schooling goes up by one?
Watch out!
Don't mix up the slope and the y-intercept!
We're looking at changes, so focus on the slope.
STEP 2
1. Understand the Equation
2. Interpret the Slope
STEP 3
Alright, so we've got this cool equation, .
This tells us how the number of pregnancies () changes based on the years of schooling ().
It's a linear equation, which means it's a straight line!
STEP 4
Remember, a linear equation is in the form .
Here, is the slope (how steep the line is) and is the y-intercept (where the line crosses the y-axis).
STEP 5
Let's match our equation, , to the general form.
Notice, we can rewrite our equation as .
Now, it's super clear that our slope is and our y-intercept is .
STEP 6
The slope tells us how much (number of pregnancies) changes when (years of schooling) increases by one.
In our case, the slope is .
STEP 7
A negative slope means that as increases, decreases.
So, as years of schooling increase, the number of pregnancies decreases.
STEP 8
Specifically, our slope is .
This means that for every one year increase in schooling, the number of pregnancies tends to decrease by 3.
Boom!
SOLUTION
The correct interpretation is: When the amount of schooling increases by one year, the number of pregnancies tends to decrease by 3.