1. Section 2-4 Using Linear Models 10/3/17

2. Dependent Variable: y
Independent Variable: x

3. Scatter Plot:
A graph of ordered pairs that represent 2 different sets of data.
Trend Line:
A line that APPROXIMATES a relationship between data.
You can use trend lines to make predictions about the data in the future.
(It’s sometimes called a “line of best fit”)

4. There are two kinds of questions in
Section 2-4: those with points & those w/out.
Without Points
You have already saved up $250 toward a new car, and save $50 per month as well. Write an equation to model the amount saved after x months.
y is dependent & represents money saved
x is independent & represents months

5. y is dependent and represents money saved
You have already saved up $250 toward a new car, and save $50 per month as well. Write an equation to model the amount saved after x months.
y is dependent and represents money saved
x is independent and represents months
So the EQ is….
y = 50x + 250
y-int
What is the y-int?
What does it represent?
It means after 0 months, only $250 is saved.

6. With Points
In Professor Patrick’s two Calculus classes he notices there are few people with red hair. One class has 1 redhead out of 20 students. The other, 3 out of 80.
Write an equation to model the situation, and predict how many redheads in his Probability class of 200.
Write the points. (1, 20), (3, 80)
Now find the slope:
m = 80 – 20 = 30
3 – 1
Hmmm what formula will I use to make the EQ when I have a POINT and a SLOPE??!!...

7. The point-slope formula of course!
y – y1 = m(x – x1)
I used the point (1, 20) but the other is also fine.
y – 20 = 30(x – 1)
To predict how many redheads in his Probability class of 200 students, put 200 in for y and solve for x.
200 – 20 = 30(x – 1)
180 = 30x – 30
210 = 30x
7 = x
So, he would expect 7 in the class of 200 to have red hair.

8. No getting frustrated then quitting! No excuses! Try your best.
Using a Trend Line in a scatter plot to make a prediction
PAGE 81 #1 – 8, 11
No getting frustrated then quitting! No excuses! Try your best.
Approx. Sign Legibility Distance of a 75-year old driver:
312 ft or so