# How to find the exponential regression formula by using a graphing calculator

Updated on December 29, 2012

This is the note from Math 141 (Precalculus) I took at GRCC in Fall 2012.

Sometimes you will be given a series of points and want to find the exponential regression formula by using a graphing calculator. Easy way to do so is just follow the steps below:

I am going to use the data given below to determine the exponential regression formula.

X
-1
1
2
3
5
7
Y
3.4
7.5
10.3
16.4
36.4
82.4

On the any graphing calculator, such as TI83, go to STAT then scroll down to EDIT and press enter. Put the X values in the LIST L1 and the corresponding Y values in L2 in order.

In this case, -1, 1, 2, 3, 5, and 7 are the values of X and 3.4, 7.5, 10.3, 16.4, 36.4, and 82.4 are the values of Y. Make sure they all match up so the ordered pairs are the same as your data.

Hit the STAT again and scroll right to the CALC menu and scroll down until you get to ExpReg. Press ENTER twice and the the calculator will show the regression of the data you entered.

ExpReg

y=ab^x; a=4.940686086, b=1.490880116

Also be able to get the value of r. The closer the value is to 1, the better fit the regression is to the data.
To get the value of r, hit the VARS and scroll down to the Statistics then enter. Scroll right to the EQ and scroll down until you get to r then enter. You should have the value of r.

r=.9995829116

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