How_To_Be_Good_At_Math

STATISTICS • THE MEAN 277

The mean

When people talk about the average, they are usually talking

about the mean. We work it out by adding up the individual

values in a group and dividing the total by the number of values.

Now divide the total

height by the number

of giraffes: 17.5 ÷ 5 = 3.5

Monday

18°

Saturday

18°

Wednesday

22°

Thursday Friday

20°

Sunday

Tuesday

15°

23°

17°

3.8 m

3.7 m

4.4 m

2.8 m 2.8 m

Let’s find the mean

height of this group

of five giraffes.

First, we add up all the

heights of the giraffes:

3.7 + 4.4 + 2.8 + 2.8 + 3.8 = 17.5

So, the mean height of

these giraffes is 3.5 m.

Is it hot today?

Or just average?

Weather forecasts often

mention average or mean

temperatures. Here are

the midday temperatures

for a week. Let’s work out

the mean temperature.

TRY IT OUT

First, add up all the

individual temperatures.

Then count the number

of temperatures.

To find the mean,

divide the total

of the temperatures

by the number of

temperatures.

Answer on page 320

MEAN

0

4 m

3 m

1 m

5 m

2 m

HEIGHT

The mean is the sum

of all values divided by the

number of values.

276_277_Averages_mean.indd 277 29/02/2016 18:06