Page 399 - Math Smart - 7

Bella records the number of times she hears her favourite Number of times song is
Frequency
song each week. played per week
Calculate the estimate of the mean number of times her 0-4 2
favourite song plays each week. Round your answer to the 5-9 8
10-14 11
nearest whole number.
15-19 4
20-24 2

Dina works at a call centre. She records the duration of Call duration (min) Frequency
each telephone call for a month.
0£t< 10 28
a) How many calls did Dina receive during the month? 10<t<20 22
20£t<30 18
b) Which call duration was the most common?
30 £ t < 40 17
c) Calculate an estimate of the mean duration of one
40 5 t < 50 20
telephone call during the month.
50 £ t < 60 3
60£t<70 13
70 s t < 80 2

Elsa conducts a survey to find out how many millilitres Millilitres of water Frequency
of water teeneagers drink each day. She records the 0 ^ .V < 500 12
information in the frequency table to the right. 500 <.v< 1000 35

a) What is the modal class of the data? 1000 <v< 1500 26
1500 £ v < 2000 9
b) How many teenagers are surveyed?
2000 s r < 2500 3
c) Calculate an estimate of the mean number of
2500 £ A- < 3000 1
millilitres of water consumed per day.

17.15 When to use mean, median

or mode

You have learnt that the mean, median and mode are measures of central
tendency. The objective of central tendency is to get an idea of a 'typical' value
to represent the data set. Different measures of central tendency are useful for
different sets of data.

The scores for six basketball teams in a tournament are as follows:
68, 70, 72, 74, 78, 112 hink and Share
The basketball team with a score of 112, scored much higher than the other
teams. A value that is much higher or much lower than the other values in a Did many of the
data set, is called an outlier. Since there is a high outlier in this data set, the basketball teams score
closer to the mean, or the
median is the best measure to represent the scores.
median?
Would you choose the mean or the median to represent the central tendency of
this set of data?

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