Lesson video

Hi, I'm Miss Davies.

In this lesson, we're going to be calculating the mean of a set of data that is displayed in a frequency table.

If we're calculating the mean for the number of goals scored in 27 games, that's quite a lot of adding up to do.

Let's have a go.

The total of all the number of goals is 78.

If we divide this by 27, it gives us an answer of 2.

89.

I rounded this to three significant figures.

This can be displayed a lot easier in a frequency table.

This table shows us that in five games, one goal was scored.

Two goals were scored in five games, three goals in eight games, four goals in six games and five goals in three games.

In the five games in which one goal was scored, this is a total of five goals.

In the five games where two goals were scored, this gives a total of 10 goals.

In the eight games where three goals were scored, there was a total of 24 goals.

In the next six games, there was also a total of 24 goals.

And in the last three games, there was a total of 15 goals.

The mean is calculated by dividing the total by the number of items. The total number of goals scored in the 27 games is 78.

To calculate the mean, we're going to divide 78 by 27.

This gives us an answer of 2.

89 to three significant figures.

Let's have a look at another example.

A five-sided spinner is spun and the scores are recorded.

We're going to calculate the mean score.

I've calculated the frequency multiplied by the score.

So a total number of 153 points were won in the 60 spins.

To work out the mean score, we're going to divide 153 by 60.

This gives a mean of 2.

55, but it's rounded to three significant figures.

Do we think that this spinner is fair? It isn't fair.

If it was fair, every score would have be gained 12 times, as 60 divided by five is 12.

Here is a question for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

The age multiplied by frequency total is 680.

The total number of people is 60.

To work out the mean we need to divide 680 by 60, which gives an answer of 11.

3.

Here is a question for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

The mean time spent on homework for Group X was 6.

8 hours.

For Group Y, it was seven hours.

So Group X spent less time on their homework.

Here is a question for you to try.

Pause the video to complete your task and resume once you're finished.

Here is the answer.

Marcus didn't divide by the sum of the frequencies.

The correct calculation is 430 divided by 50, which gives an answer of 8.

6.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

The mean time taken to run the race is 17.

16 seconds.

That's all for this lesson.

Thanks for watching.