## What you need to know

Things to remember:

• To find the mean of a set of numbers we add them together and divide by how many numbers we have.

In statistics, we use the “mean” to find an average of a set of date. It is sometimes called the “expected value”, because it tells us what we’d expect to get.

The mean is quite nice, because it’s easy to find. We do this by adding up all of our and dividing it by how many numbers we have, so it only takes two steps.

Find the mean of the following set of data

3          1          8          6          2

Step 1: Add up all of the data (all of the numbers).

$$3+1+8+6+2 =20$$

Step 2: Divide the number you got in Step 1 by how many numbers there are.

$$20\div5=4$$

To, the mean of this set of data is 4.

This works for any amount of numbers, even just 2!

Find the mean of the following set of data

2                      8

Step 1: Add up all of the data (all of the numbers).

$$2+8=10$$

Step 2: Divide the number you got in Step 1 by how many numbers there are.

$$10\div2=5$$

But really, this is just finding the number between 2 and 8.

## Example Questions

#### Question 1: Find the mean of the following set of data5          2          1          4

Step 1: Add up all of the data (all of the numbers).

$$5+2+1+4=12$$

Step 2: Divide the number you got in Step 1 by how many numbers there are.

$$12\div4=3$$

The mean is 3.

#### Question 2: Find the mean of the following set of data6          8          2          8          1          5

Step 1: Add up all of the data (all of the numbers).

$$6+8+2+8+1+5=30$$

Step 2: Divide the number you got in Step 1 by how many numbers there are.

$$30\div6=5$$

The mean is 5.