Probability and Statistics > Basic Statistics> > How to Find the Mean

## How to Find the Mean: Overview

The

**mean**in mathematics can have several meanings, but in statistics it is always the

**average**. The mean is found by adding the numbers in a data set and then dividing by the number of items. For example, to find the mean of 1, 2, and 3:

- 1 + 2 + 3 = 6
- 6 / 3 = 2.

Use a calculator to find the mean to avoid making errors.

## How to Find the Mean of a Data Set: Steps.

**Sample problem 1:** Find the mean for the following set of numbers: 1, 5, 6, 8, 3, 5, 11, 19, 21, 34.

Step 1: Add up all of your numbers:

1 + 5 + 6 + 8 + 3 + 5 + 11 + 19 + 21 + 34 = 113.

Step 2:

**Count the number of items in your set.**There are

**10**numbers in the set: 1, 5, 6, 8, 3, 5, 11, 19, 21, 34.

Step 3:

**Divide the number you calculated in Step 1 by the number you found in Step 2**.

Mean = 113 / 10.

**The mean for this data set is 11.3.**

**Sample problem 2:** Find the mean for this set of numbers: 101, 135, 156, 156.1, 190.5:

Step 1: Sum (add up) all of your numbers:

101 + 135 + 156 + 156.1 + 190.5 = 738.6.

Step 2:

**Count the number of items in your set.**There are

**5**numbers in the set.

Step 3:

**Divide the number you calculated in Step 1 by the number you found in Step 2**.

Mean = 738.6 / 5 = 147.72.

**The mean for this data set is 147.72.**

*That’s it!*

## Find the Mean on the TI 89 Graphing Calculator

Instead of adding lists of numbers and trying to remember formulas, the TI-89 does the work for you and keeps the formulas in its memory. While it’s important to know the basics (for example, what a mean is and how it’s calculated), it isn’t necessary (or fun!) to do the same types of calculations manually over and over again. Find the TI 89 mean with these easy steps.

## TI 89 Mean: Steps

Watch the video or read the steps below:

**Sample problem:** Find the mean of the following set of data: 12, 23, 78, 98, 121, 342, 88, 7, 27.

**Step 1:** Get to the HOME*screen* by pressing the HOME button. You can also access the home screen from the APPS menu. Click APPS and then use the arrow keys to scroll to the HOME icon. Press ENTER.

**Step 2:** Press the CATALOG *key* (located below the APPS key).

**Step 3:** *Press the *ALPHA *key* (a white key to the left of the Apps key, then the number 5. This is you actually entering the letter ‘M’ which will bring you to the letter “M” in the catalog.

**Step 4:** *Scroll down to* “mean(” *and press* ENTER.

**Step 5:** *Press the *2nd key (a light blue key at the top left) then the ( key. This enters a curly bracket.

**Step 6:** *Enter your data set and separate each number by a comma; *the comma key is above the 9 key. In our example, you’ll enter 12, 23, 78, 98, 121, 342, 88, 7, 27.

**Step 7:** *Press the* 2nd *key, then the ).*

**Step 8:** *Press* ENTER. Your answer may be given as a fraction: **796/9** (that’s the exact answer). To get a decimal answer, press the ♦ diamond key then ENTER to get **88.4444**.

Lost your guidebook? You can download a new one from the TI website here.

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