Working with charts, graphs and tables
Working with charts, graphs and tables

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Working with charts, graphs and tables

4.8.1 Mean

The mean is found by adding up all the values in a set of numbers and dividing by the total number of values in the set. This is what is usually meant by the word ‘average’.

For example, if a company tests a sample of the batteries it manufactures to determine the lifetime of each battery, the mean result would be appropriate as a measure of the possible lifetime any of the batteries and could be used to promote the product.

Activity 12

A sample of 15 batteries was tested. The batteries lasted, in hours:

23, 28, 25, 30, 18, 29, 23, 19, 30, 24, 25, 21, 26, 25, 23

  1. Calculate the mean life of a battery, correct to one decimal place (i.e. with one figure after the decimal point).

  2. How many hours of life will the company claim?


  1. Adding up all the values gives 369. Dividing 369 by 15 gives 24.6.

  2. The company is likely to claim an average battery life of 25 hours (24.6 rounded up to the nearest hour).

However, the mean is not always a good representation of the data. To illustrate this, consider the annual salaries of the people employed by a small company. The salaries, in euros, are:

22 000, 22 000, 25 000, 28 000, 35 000, 65 000, 92 000

The mean salary = 289 000 ÷ 7 = 41 286 euros (approximately). Here, however, the mean is very misleading because the two highest salaries raise the mean considerably. You might like to confirm this by calculating the mean of just the five lowest salaries.

Skip Your course resources

Take your learning further371

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371