Finding a critical value and reading a z-table are an essential part of elementary statistics. Critical values are used for hypothesis tests, and can help you use the standard normal model to make predictions about data. The TI-89 Titanium graphing calculator makes light work of finding these values, because of its built in z-table. The TI-89 Titanium’s Stats/List Editor contains a simple menu where you can look up Z Score in seconds. This article shows you how to find the z-score for a critical value in a left tail. As the normal distribution curve is symmetrical, this will also be the area in a right tail as well. Not sure if your test is a left tailed or right tailed? See “Left Tailed Test or Right Tailed” to help you decide.
Note that you must have the Stats/List Editor installed to be able to make a TI-89 frequency distribution using these instructions.
Z Score TI 89: Steps
Sample problem: find the z score for α = .012 for a left-tailed test on a standard normal distribution curve.
Step 1: Press Apps, scroll to the Stats/List Editor, and press ENTER.
If you don’t see the Stats/List Editor, you can download it here. It’s an official TI app and you’ll need to transfer it to your calculator using the cable that originally came with your TI-89.
Step 2: Press F5 2 1, to get to the Inverse Normal screen.
Step 3: Enter .012 in the Area box.
Step 5: Press ENTER.
Step 6: Read the result: the calculator should state “Inverse = -2.25713“. This is your z score.
That’s how to find a z score TI 89!
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