How To Calculate Residuals On Ti 84

Okay, let's talk about something *riveting*: residuals on your TI-84. Yes, that's right. I said it. I know what you're thinking. But trust me, there's a way to make this... less painful.

The List Life

First, enter your data. It goes in lists, of course! List 1 and List 2 are your best friends. Or maybe your frenemies, depending on how math is treating you today.

Now, hit that magical STAT button. Prepare to be amazed. Choose "Edit" and punch in your x-values (List 1) and y-values (List 2).

Regression Revelation

Time for regression! Again, press STAT. This time, go to "CALC." So many choices! Linear regression, quadratic regression... the possibilities are endless (sort of).

Pick your poison. Let's say you choose "LinReg(ax+b)." Sounds fancy, right? It's not. It's just a line.

Here's the thing that makes some people mad. You need to tell the calculator where to store the regression equation. Because why not make it complicated?

After "LinReg(ax+b)", you'll put a comma. Now comes the trick. Hit VARS, then "Y-VARS", then "Function", and then choose Y1. This puts the equation in Y1.

Your screen should now read something like "LinReg(ax+b) L1, L2, Y1". Press enter. Magic! You'll see the a and b values for your line. Write them down if you must.

Residual Roundup

This is where it gets *really* exciting. (Okay, maybe not). The calculator has been secretly saving your residuals! It's like a mathematical hoarder.

These residuals are stored in a list called, creatively, RESID. Where is this list you ask? It's lurking. Press STAT, then "Edit". You may not see it initially.

Scroll all the way to the right. Keep going! There it is: RESID. It's probably full of decimals. Yay!

List Manipulation

Now, here's where you can actually see the residual values. You can view them just by looking at the RESID list. Or, you can plot them.

To plot them, hit 2nd then Y= (STAT PLOT). Choose Plot1. Turn it ON. Make the Xlist L1. Make the Ylist RESID.

Hit ZOOM, then ZoomStat (option 9). Boom! A residual plot. Is it random? Does it have a pattern? That's for another day. I have an unpopular opinion: residual plots are never perfectly random.

Or... you can put the residuals into List3. Maybe you want to do calculations with them. I won't judge.

Highlight L3. Then press 2nd then LIST (STAT). Scroll down (or up) until you find "RESID". Select it. Press Enter.

Now List3 is filled with those lovely residual values. You're welcome.

My Unpopular Opinion

Here's my totally controversial take: You don't *need* to understand everything about residuals to pass your stats class. Just know the steps! Memorize! Survive!

I know, I know. "Understanding is important!" But sometimes, you just need to get through the exam. We've all been there.

So, there you have it. Residuals on your TI-84, demystified (sort of). Go forth and calculate! And remember, it's okay if you don't *love* it. Just get it done.