Considering linear, quadratic, and exponential lines of best fit:

Question

If you're studying a set of data, how can you decide which of those three types of model would be most appropriate for the data?

Answer 1

linear: constant difference
quadratic: constant 2nd differences
exponential: constant ratio over equal intervals

Answer 2

Steve, thank you, but what do you mean constant 2nd differences? And constant ratio over equal intervals? For me, the difference between linear and exponential is that linear go up/down at a constant amount by adding that same constant amount. Exponential goes up/down by multiplying that same constant amount.

Answer 3

x _y____y(n)-y(n-1) ___ next diff

1__0______
2__5______ 5
3__10_____ 5____________0
4__15_____ 5____________0
5__20_____ 5____________0
6__25______5____________0
THAT is constant diff
now
x _y____y(n)-y(n-1) ___ next diff

1__1______
2__4______ 3
3__9_______5____________ 2
4__16 ____ 7____________ 2
5__25_____ 9_____________2
6__36______11____________2
THAT is constant difference of difference - Get it?