Cambridge International Mathematics

Continuous data (Chapter 17) 357

Example 2 Self Tutor

The table below shows masses of parcels received by a company during one week.

Mass (kg) 06 m< 1 16 m< 2 26 m< 3 36 m< 6 66 m< 10

Number of parcels 20 30 15 60 40

a Draw a histogram to represent the data.

b Find the modal class interval.

c Use a graphics calculator to estimate the mean mass of the parcels received.

Mass (mkg) Frequency CIW Frequency density

06 m< 1 20 1 20

16 m< 2 30 1 30

26 m< 3 15 1 15

36 m< 6 60 3 20

66 m< 10 40 4 10

a Histogram showing masses of parcels b

c Middle value (x) Frequency (f)

0 : 5 20

1 : 5 30

2 : 5 15

4 : 5 60

8 40

mean¼ 4 : 14 kg (calculator)

Example 3 Self Tutor

The times taken for students to complete a cross-country run were measured. The results were:

Time (tmin) 206 t< 23 236 t< 26 266 t< 31

Frequency 27 51 100

a Draw a histogram to represent the data.

b Find the modal class.

c Estimate the mean time for students to run the event.

Time (tmin) Frequency CIW Frequency density

206 t< 23 27 3 9

236 t< 26 51 3 17

266 t< 31 100 5 20

75 10 7 : 5

CIW means

class interval width.

24681012

0

10

20

30

frequencydensity

mass ( kg)m

key

represents

5 parcels

316 t< 41

75

316 t< 41

The modal class is 16 m< 2.

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Y:\HAESE\IGCSE01\IG01_17\357IGCSE01_17.CDR Tuesday, 18 November 2008 11:49:13 AM PETER