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Grouped Data Averages
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TweetMr Mattock
on 20 March 2018Transcript of Grouped Data Averages
Grouped Data Averages
Starter
Estimate of Mean
Example
L.O.  Find the modal class, median class interval and estimate of the mean for a grouped frequency table.
Why is it not
possible to find
averages of this
data?
What can we say about the data?
Starter
Why is it not
possible to find
averages of this
data? 
We don't have the exact values.
What can we say about the data?

Most people between 60 and 70 kg
midpoint
m x f
Estimate of Mean
midpoint
m x f
45 90
55 825
65 1235
75 750
85 85
Total weight estimate = 2985 kg
Mean weight estimate = 63.5 kg
Find an estimate of the
mean number of yellow
cards.
Example
Find an estimate of the
mean number of yellow
cards.
midpoint
12
17
22
27
32
m x f
204
187
154
108
32
Total cards
estimate
=685
Mean number of cards estimate = 685/40 = 17.125
Main Activity 1
Estimate the mean of a table in the RAG sheet.
Main Activity Answers
Red  130 x 2 + 150 x 5 + 170 x 18 + 190 x 7 =
5400 cm. 5400/32 = 168.75 cm
Amber  51.5 x 36 + 54.5 x 48 + 57.5 x 28 + 60.5 x 8 =
6564 mm. 6564/120 = 54.7 mm.
Green  12.5 x 7 + 16.5 x 13 + 20.5 x 8 + 24.5 x 3 + 28.5 x 1
= 568 marks. 568/32 = 17.75 marks.
Median Class Interval
In which interval does the median lie?
Median Class Interval
In which interval does the median lie?
2
17
36
46
47
47 people  middle person = 48/2 = 24th person.
24th person in the interval 60 < w < 70
Example
Example
17
28
35
39
40
40
weeks
Middle = 20th and 21st weeks.
Both 1519 cards.
Main Activity 2
Find the median class interval for a table
on your RAG sheet.
Red  32 people; middle = 16th and 17th pupil; both are in the interval 160 < h < 180.
Amber  120 fingers; middle = 61st and 62nd; both are in the interval 53 < s < 56
Main Activity 2 Answers
Green  32 people; middle 16th and 17th people; both are in the interval 15  18.
Dice of Ultimate Power
1) Give a key word for the lesson.
2) Summarise one key point for the
lesson.
3) Explain one thing you have learned this
lesson.
4) State one thing you still don't understand following this lesson.
5) Suggest one thing you would like to find out
based on this lesson.
6) Free choice from 1 to 5, or another you make
up.
Main Activity 2
Find the median class interval for a table
on your RAG sheet.
32 people, so middle are 16th and 17th. Both in the interval 160 < h < 180
120 fingers, so middle is 60 and 61. Both in the interval 53 < s < 56.
32 people, so middle are 16th and 17th. Both in the interval 1518
Key
Examples
Activity
Answers
Activities
Worked
Example
Worked
Example
Worked
Example
Worked
Example
Full transcriptStarter
Estimate of Mean
Example
L.O.  Find the modal class, median class interval and estimate of the mean for a grouped frequency table.
Why is it not
possible to find
averages of this
data?
What can we say about the data?
Starter
Why is it not
possible to find
averages of this
data? 
We don't have the exact values.
What can we say about the data?

Most people between 60 and 70 kg
midpoint
m x f
Estimate of Mean
midpoint
m x f
45 90
55 825
65 1235
75 750
85 85
Total weight estimate = 2985 kg
Mean weight estimate = 63.5 kg
Find an estimate of the
mean number of yellow
cards.
Example
Find an estimate of the
mean number of yellow
cards.
midpoint
12
17
22
27
32
m x f
204
187
154
108
32
Total cards
estimate
=685
Mean number of cards estimate = 685/40 = 17.125
Main Activity 1
Estimate the mean of a table in the RAG sheet.
Main Activity Answers
Red  130 x 2 + 150 x 5 + 170 x 18 + 190 x 7 =
5400 cm. 5400/32 = 168.75 cm
Amber  51.5 x 36 + 54.5 x 48 + 57.5 x 28 + 60.5 x 8 =
6564 mm. 6564/120 = 54.7 mm.
Green  12.5 x 7 + 16.5 x 13 + 20.5 x 8 + 24.5 x 3 + 28.5 x 1
= 568 marks. 568/32 = 17.75 marks.
Median Class Interval
In which interval does the median lie?
Median Class Interval
In which interval does the median lie?
2
17
36
46
47
47 people  middle person = 48/2 = 24th person.
24th person in the interval 60 < w < 70
Example
Example
17
28
35
39
40
40
weeks
Middle = 20th and 21st weeks.
Both 1519 cards.
Main Activity 2
Find the median class interval for a table
on your RAG sheet.
Red  32 people; middle = 16th and 17th pupil; both are in the interval 160 < h < 180.
Amber  120 fingers; middle = 61st and 62nd; both are in the interval 53 < s < 56
Main Activity 2 Answers
Green  32 people; middle 16th and 17th people; both are in the interval 15  18.
Dice of Ultimate Power
1) Give a key word for the lesson.
2) Summarise one key point for the
lesson.
3) Explain one thing you have learned this
lesson.
4) State one thing you still don't understand following this lesson.
5) Suggest one thing you would like to find out
based on this lesson.
6) Free choice from 1 to 5, or another you make
up.
Main Activity 2
Find the median class interval for a table
on your RAG sheet.
32 people, so middle are 16th and 17th. Both in the interval 160 < h < 180
120 fingers, so middle is 60 and 61. Both in the interval 53 < s < 56.
32 people, so middle are 16th and 17th. Both in the interval 1518
Key
Examples
Activity
Answers
Activities
Worked
Example
Worked
Example
Worked
Example
Worked
Example