Inspired by Math Teacher Mambo’s “that super awesome functionality been on my calculator for YEARS and I never knew about it” post, I decided to post something that I learned this year which had a similar effect on me.

(You probably already know this if you teach statistics. Maybe everyone knows this.)

**ENTERING REGRESSION EQUATIONS AUTOMATICALLY IN THE EQUATION LINE OF A TI-83/4**

The short version: when doing any form of regression, you end up getting the coefficients displayed like this (below left). However if you wanted to graph that cubic, I had my students manually write down every coefficient on a piece of scrap paper, and then type it into the equation screen (bottom right). To make matters worse, you had to write down a good number of digits so you wouldn’t lose too much accuracy. I couldn’t find a way around it. What a pain, and students would make mistakes with all the copying, followed by typing the equation in Y1.

Of course you all knew that the “duh” moment came. The other Algebra II teacher taught me this simpler, foolproof way. It automatically enters the regression equation into Y1:

When you do the CubicReg command, you need to add the Y1 argument (above left). (You can get Y1 by following key sequence: VARS, Y-VARS, FUNCTION, Y1). Then it’s automatically entered in Y1 (above right).

I can’t believe no one ever told me that. I can’t believe I made my students write down the coefficients by hand.

I made a jing video of how to do this. Sorry about my voice. I hate hearing myself recorded. One of the many things that terrify me.

Vodpod videos no longer available.

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Note: I republished this post, because I found a way to embed video in it. For some reason, I wasn’t able to embed this video in my original post.

Comment from mathfaery on original post:

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That’s pretty cool. I normally find the regression equation first. Then when I want to graph it, in Y1, I press VARS, choose 5:Statistics, select EQ, and then 1:RegEQ. This inputs the equation into Y1 also with no need to copy down all of the decimal values and hoping that you reenter them correctly.