Question

how do you know whether to perform a linear regression or a quadratic regression for a given set of data

Answer 1

1. If the first difference is the same value, the model will be linear.

2. If the second difference is the same value, the model will be quadratic.

Answer 2

if you have a date set that changes linearly(in a line) then do a Lin reg if it appears to curve and is not one to one then do a quad reg. this is best done on your calculator