NAME: ___________________________	Stats	
Scatterplots – Finding best fit line	DATE: October 5, 2015	

Draw a line through your data as best you can.  Find two points that the line goes through and then find its equation.  

So if the line goes through (4,5) and (8,-23)

Remember all lines can be expressed as 
y=mx+b 
where
	m=slope
	b = y-intercept

Steps:

1.	Find the slope.
a.	

2.	Re-write y=mx+b with the slope (which is m).
3.	Find the y intercept.
a.	Now use one point and substitute it into the equation for y and x and solve for b

4.	Re-write y=mx+b with the y-intercept (which is b).

	Our points are (4,5) and (8,-23)

1. 

2.   y=-7x+b

3. Lets substitute (4,5) in and solve for b
y=-7x+b	
Start with our equation	

(5) = -7(4) +b	
4 is x, and 5 is y	

5   =  -28+b	
Simplify	

+28   +28	
Add 28 on each side to get b alone	

33 =        b	
b, the y-intercept is 33	

4. y=-7x+33