**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 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 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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This was helpful as well, this is much better than doing the math by hand! Thanks!

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…).

Thanks for the info, Zok!