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## Critical z value TI 83

A critical value in hypothesis testing separates the region where the hypothesis will be rejected from the region where the hypothesis will not be rejected. You could use the equation above to find the z-score, but it’s not the easiest equation to look at! With a little **arithmetic**, you can look up a critical value in a z-table, or you can use the **InvNorm** function on the **TI-83 graphing calculator**.

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## Critical z value TI 83: Steps

**Sample Problem**: An end of semester exam is normally distributed with a mean of 85 and a standard deviation of 10. Find the z score at the 90th percentile with the InvNorm function

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**Step 1:** Press 2nd VARS 3. This displays **InvNorm(** on the home screen.

**Step 2:** Type . 9 0 , 8 5 , 1 0.

**Step 3:** Press the ) button.

Your display should read **InvNorm(.9, 85, 1, 0)**.

**Step 4:** Press ENTER. This returns **97.82**. That means that 90% of students will have scores below 97.82.

That’s it! Like the explanation?

That’s how to find a Critical z value TI 83!

**Tip**: The first entry on InvNorm should be a number between 0 and 1.

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