Finding critical values 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 critical 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 you your test is a left tailed or right tailed? See “Left Tailed Test or Right Tailed” to help you decide.
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.
Step 2: Press F5 2 1, to get to the Inverse Normal screen.
Step 3: Enter .012 in the Area box.
Step 4: Enter 0 for the mean, μ and 1 for the standard deviation, σ.
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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