TC3 → Stan Brown → TI-83/84/89 → TI-83/84 Lists for Paired t Test
revised 23 Dec 2011

# List Operations for Paired t Test on TI-83/84

Summary: In a paired t test, you find the difference between data pairs. That can be tedious, and it’s easy to drop a minus sign. This page shows you how to use TI-83/84 list operations to find the differences.

PersonBeforeAfter
17883
26466
37077
47174
57075
66871

Consider the data at left, which come from the example on Dabes & Janik’s Statistics Manual (1999), page 264. Heart rate is recorded for six people before and half an hour after drinking two cups of coffee. H1 is μd>0, and α=.01.

To perform the paired t test, you define the difference

d = After − Before

and then compute the differences. For this particular data set, all the differences are positive. But usually you will have a few negatives among the positives. It’s easy to overlook a minus sign when taking differences for many pairs of numbers, but of course that makes your t test completely bogus. Your TI-83/84 can help.

 Store the “Before” numbers in L1 and the “After” numbers in L2. [`STAT`] [`1`]; cursor to `L1` column heading, press [`CLEAR`] [`ENTER`], and enter the “Before” numbers.   Cursor to `L2` column heading, press [`CLEAR`] [`ENTER`], and enter the “After” numbers. You want to get the column of differences, After−Before, That’s the same as L2−L1, which is the formula for L3. Cursor to `L3` column heading. Enter the formula, [`2nd` `2` makes `L2`] [`−`] [`2nd` `1` makes `L1`] [`ENTER`].

Notice that any excess numbers in L3, beyond the length of L1 and L2, are automatically removed. (The formula might be L1−L2 or L2−L1, depending on how you defined your d.)

Now you can proceed with the t test, using the data in L3.

 Find sample mean and standard deviation. [`STAT`] [`►`] [`1`] for `1-VarStats`, then [`2nd` `3` makes `L3`]. Since the sample statistics are automatically pasted to the t test screen, you don’t need to copy them. Just enter the μ and the “>” from your H1. [`STAT`] [`◄`] [`2`] for `T-Test`  Enter 0 for μo. Skip past x̅, s, and n. Enter >μo, then select `CALCULATE` or `DRAW`.

How would you show your work for this problem? Here’s a sample:

“before” in L1, “after” in L2, L3=L2-L1
1-VarStats L3
T-Test inputs: μo: 0, : 4.17, s: 1.83, n: 6, μ >μo
Outputs: t = 5.5624, p = .0013

Now practice with any of the examples in your textbook.

This page is used in instruction at Tompkins Cortland Community College in Dryden, New York; it’s not an official statement of the College. Please visit www.tc3.edu/instruct/sbrown/ to report errors or ask to copy it.

For updates and new info, go to http://www.tc3.edu/instruct/sbrown/ti83/