TI 83 calculator for statistics > T distribution on a TI 83

## T distribution on a TI 83: Overview

The **T distribution** (sometimes called Student’s T distribution) is actually a set of distributions, differentiated by the degrees of freedom (df). There’s only a slight difference between the t distribution and a normal curve; In general you use a normal distribution whenever you can. But in some situations (like a very small sample), you have to use the t-distribution to find probabilities.

Take a look at a traditional textbook T table, and you’ll actually find *many* T tables, which can be a little overwhelming. Instead of poring over tables, you can use a **TI 83 graphing calculator** to assist you in finding T distribution values.

You might be asked to find the area under a T curve, or (like Z scores), you might be given a certain area and asked to find the T score.

## T distribution on a TI 83: Steps

**Sample problem**: Find the area under a T curve with degrees of freedom 10 for P( 1 ≤ X ≤ 2 ). Use the t distribution on a TI 83.

**Step 1:** Press 2nd VARS 5 to select **tcdf(**.

**Step 2:** Enter the lower and upper bounds, and the degrees of freedom. The lower bound is the lowest number and the upper bound is the highest number: 1 , 2 , 1 0 )

Your screen should now read **tcdf(1,2,10)**

**Step 3:** Press ENTER. The answer is **.133752549**, or about **13.38%**.

That’s how to find a T distribution on a TI 83!

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