Page 108 - MAT KS3 Y8 Cambridge CheckPoint

10.2 Calculating statistics from grouped or continuous data

3 This table shows the heights of 60 young children.

Height (cm) 80–84 85–89 90–94 95–99 100–104 105–109
Frequency 10 20 15 10 3 2

a Estimate the median height.
b What is the largest possible value of the range?
c Estimate the mean height.
4 This table shows the lengths of 50 text messages sent from a mobile phone.

Number of characters 1–10 11–20 21–30 31–40 41–50 51–60
Frequency 10 8 12 16 3 1

a Write down the modal class.
b Explain why the median must be more than 20.
c Explain why the range must be more than 40.
d Estimate the mean length of a text message.

5 A survey of the time people spent travelling Journey time Frequency
to work one morning gave these results. Up to 30 minutes 15
a How many people were involved in the
30 minutes or more but less than one hour 30
survey?
1
b Write down the modal class. One hour of more but less than 1 hours 10
2
c Estimate the median journey time.
1
1 hours or more but less than two hours
d Estimate the mean journey time. 2 2

6 A group of people took part in a test to see how
How long can you hold your breath?
long they could hold their breath.
The results are shown in this frequency diagram. 40
a Write down the modal class. 35
b How many people were involved? 30
c Estmate the median time. Frequency 25
d Estimate the mean. 20
e Maha asked: ‘What is the average time?’ 15
10
What is the best answer to use?
5
Give a reason for your answer.
0 40 50 60 70 80 90
Time (seconds)
10 people held their breath
for 40–50 seconds.

106 10 Processing and presenting data