Question 405762
Consider the data below to find the equation of the best fit line: 
x,y = (1,85); (2,65); (3,70); (4,90); (5,75). 

----
It's not linear because y does not increase or
decrease in a consistent manner.
----
Try a quadratic or cubic or other regression program
and look at the r-values generated. The closer to 
1 the better the fit.
=====================
cheers,
Stan H.