How To Do Chi Squared On Ti 84

So you’ve got a TI-84 and a chi-squared problem. Don’t panic. It’s easier than assembling IKEA furniture—though that’s a low bar.

First, figure out which chi-squared you need. Goodness of fit? Independence? They live in different menus. No shame in mixing them up. I did last Tuesday.

The Goodness of Fit Test

This one compares observed counts to expected counts. Put your observed numbers in L1. Put your expected numbers in L2.

Hit STAT, then arrow right to TESTS. Scroll down to X^2 GOF-Test. Press ENTER. It’s like ordering a secret menu item.

It asks for Observed and Expected lists. Make sure L1 and L2 are selected. Then it wants degrees of freedom. That’s df = number of categories minus one. Enter it manually.

Select Calculate. You’ll get a chi-square statistic, a p-value, and your df. If p < 0.05, reject the null. Boom. You’re a statistician.

The Independence Test

This one checks if two categorical variables are related. You need a matrix. Press 2nd, then MATRX (above the x^-1 key). Choose Edit [A].

Enter the dimensions: rows and columns. Then fill in the inner counts. Don’t worry about totals—the calculator adds those. Just type the numbers and press ENTER after each.

Quit out. Go to STAT, TESTS, scroll to X^2-Test. ENTER. It asks for the Observed matrix. Choose [A]. Leave Expected as [B] or whatever. Then Calculate.

Output: chi-square, p-value, df. Your df is (rows - 1) times (columns - 1). Same decision rule as before. Small p means variables are linked. Big p means they’re independent.

Calculating Chi Square Upper Tail Area (TI-83 & TI-84) - YouTube

Reading the Output Without Crying

The p-value is your friend. It tells you how surprising your data is. If p is tiny, something’s going on. If p is huge, yawn—no relationship.

Also check your expected counts. Every single one should be at least 5. If not, chi-squared gets grumpy. It might give you a warning. Or just lie to you.

Common Goofs

Putting expected counts in the wrong list. Forgetting to define your matrix. Using percentages instead of counts. Counts, people. Counts.

If you get an error, check your lists. Maybe you left a stray number from last week’s homework. Or your matrix dimensions are off. It happens to the best of us.

One more thing: the TI-84 doesn’t do Fisher’s exact test. So if your expected counts are tiny, maybe switch to that. But that’s a different coffee chat.

Before You Start: Clear Those Lists!

Old data can haunt you. Press 2nd then + (MEM). Choose ClrAllLists. Or manually go to STAT > Edit and clear L1, L2, etc. A clean slate saves headaches.

What About a 2x2 Table?

Independence test works fine. But some folks prefer the 2-PropZTest for proportions. That’s a different beast. For chi-squared, just follow the matrix steps. It handles any size.

How to Interpret the Chi-Square Statistic

Big chi-square means observed and expected are far apart. Small chi-square means they match nicely. The p-value translates that into probability. Don’t just stare at the number.

Finding Chi-square critical values with the TI-84 - YouTube

Pro Tip: Store Your Expected Counts

When you run the GOF test, the calculator can store expected counts. It usually puts them in L3 or something. Check the menu. That way you can compare later.

What If You Only Have Summary Data?

You can type observed counts directly into a list. No need to have raw data. Just counts per category. Same for matrix—just the cell counts. Easy peasy.

Don’t Forget the Null Hypothesis

Your null is always "no relationship" or "fits the expected." The alternative is "something's up." The p-value tells you which to believe. If p is low, the null must go.

When The Calculator Freaks Out

Sometimes you get a domain error. That usually means a negative expected count. Or you left a zero somewhere. Double-check your entries. Breathe. Try again.

A Quick Word on Sample Size

Chi-squared loves big samples. With tiny samples, your results are shaky. So if your expected counts are all 3, maybe collect more data. Or use Fisher's exact test.

So there you go. Chi-squared on a TI-84 in five minutes. Now you can impress your stats teacher. Or at least not cry during the exam. You’ve got this.

And that's it. You've officially mastered chi-squared on a TI-84. Go celebrate with a latte. You've earned it.

Remember: practice makes perfect. Try a few problems. Soon you'll be running chi-squared tests in your sleep. Well, maybe not. But close.