## How to Find a Critical Value on a Ti-89 Titanium (Left-Tailed test)

Finding critical values and reading a z-table are an essential part of statistics. Critical values are used in hypothesis testing, and can help you use the standard normal distribution graph 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 a critical value for a left-tailed tests in seconds.

Sample problem: find α = .012 for a left-tailed test on a standard normal distribution.

Step 1: Press , scroll to the Stats/List Editor, and press .

Step 2: Press , to get to the Inverse Normal screen.

Step 3: Enter .012 in the Area box.

Step 4: Enter for the mean, μ and for the standard deviation, σ.

Step 5: Press .

Step 6: Read the result: the calculator should state “Inverse = -2.25713“. This is your critical value.

Tip: If you are given a mean and standard deviation, enter them in place of 0 and 1 in Step 4.

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## 4 thoughts on “How to Find a Critical Value on a Ti-89 Titanium (Left-Tailed test)”

1. Zok

This was very helpful. Thank you!

For those trying to do this with the t-distribution, the option on the TI-89 is right below (inverse t…).