Cambridge International Mathematics

354 Continuous data (Chapter 17)

Continuous data is placed intoclass intervalswhich are usually represented byinequalities.

For example, for heights in the 140 s of centimetres we could write 1406 h< 150.

To find the mean of continuous data, we use the same method as for grouped discrete data described in

Chapter 13sectionF.

Since the data is given in intervals, our answer will only be anestimateof the mean.

Example 1 Self Tutor

Height (hcm) Frequency (f)

1306 h< 140 2

1406 h< 150 4

1506 h< 160 12

1606 h< 170 20

1706 h< 180 9

1806 h< 190 3

The heights of students (hcm) in a hockey

training squad were measured and the results

tabled:

a Estimate the mean height.

b State the modal class.

Height (hcm) Mid-value (x) Frequency (f) fx

1306 h< 140 135 2 270

1406 h< 150 145 4 580

1506 h< 160 155 12 1860

1606 h< 170 165 20 3300

1706 h< 180 175 9 1575

1806 h< 190 185 3 555

Total 50 8140

EXERCISE 17A

Weight (kg) Frequency

756 w< 80 2

806 w< 85 5

856 w< 90 8

906 w< 95 7

956 w< 100 5

1006 w< 105 1

1 A frequency table for the weights of a volleyball squad is given

alongside.

a Explain why ‘weight’ is a continuous variable.

b What is the modal class? Explain what this means.

c Describe the distribution of the data.

d Estimate the mean weight of the squad members.

A THE MEAN OF CONTINUOUS DATA [11.5]

a Mean=

P

fx

P

f

¼

8140

50

¼ 163 cm

b The modal class is

1606 h< 170 :

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Y:\HAESE\IGCSE01\IG01_17\354IGCSE01_17.CDR Monday, 20 October 2008 2:31:24 PM PETER