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Module 1: Frequency and graphs

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Mean from frequency tables - discrete data

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Mean from frequency tables - discrete data

Heather asks her friends to tell her the size of their families. She
records the data in a frequency table.

FAMILY SIZE
FREQUENCY
NUMBER OF PEOPLE

1
0
1

2
2
4

3
5
15

4
8
32

5
4
20

6
0
0

7
1
7

20
78

To calculate the mean number of people in each family we need to find the
total number of people in the survey and the number of families.

In this survey a total of 20 families were surveyed and it was found that
there were 78 people altogether.

Therefore the mean = 78/20 = 3.9 people per family.

Finding the mean from a discrete frequency table

* The frequency table tells you how many there are for each value.

* So you can work out the sub-total value of the results in each column
by multiplying: value x frequency.

* Then you can add them all to find the grand total of these sub-totals.

* The mean is just the average. So you divide the grand total by the
total frequency: total value divided by total frequency = mean.

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