1. Grouped data Objective Task Identify the modal class. [Grade C]
Sunday, 18 November 2018
Grouped data
Objective
Identify the modal class. [Grade C]
Calculate an estimate of the mean from a grouped table. [Grade C]
Task
Key Words
WS 1
Exam Qu1
By Cang Tu
Exam Qu2

2. Key words Grouped data Estimated mean Modal class
When data is grouped into classes.
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If raw data is not given, the mean of that
data is an estimated mean.
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The class that has the highest frequency.
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WS 1
Sunday, 18 November 2018
By Cang Tu
1st Slide

3. Worksheet 1 Find the modal class and the estimated mean for each table
Grade C
Qu1-2
Ans 1
Ans 2
Find the modal class and the estimated mean for each table 1) 2)
Weight, 𝒘 (kg)
Frequency, 𝒇
40<𝑤≤50 6
50<𝑤≤60 10
60<𝑤≤70 7
70<𝑤≤80 3
Mid-point, 𝒙
𝒇×𝒙 45
6 x 45 = 270 55
10 x 55 = 550 65
7 x 65 = 455 75
3 x 75 = 225
Modal
class
= 50<𝑤≤60
Estimated mean
= = 57.7kg
Total frequency = 26
Total 𝑓×𝑥 = 1500
Modal
class
= 20<𝑙≤25
Length, 𝒍 (cm)
Frequency, 𝒇
20<𝑙≤25 14
25<𝑙≤30 5
30<𝑙≤35 3
Mid-point, 𝒙
𝒇×𝒙
22.5
14 x 22.5 = 315
27.5
5 x 27.5 = 137.5
32.5
3 x = 97.5
Estimated mean
= = 25cm
Exam Qu1
Total frequency = 22
Total 𝑓×𝑥 = 550
Sunday, 18 November 2018
By Cang Tu
1st Slide

4. Exam Qu 1 Caleb measures the heights of 30 plants
Ans 1
Caleb measures the heights of 30 plants
The table gives some information about the heights, h cm, of the plants.
Work out an estimate for the mean height of a plant
………………..cm (4 marks, C)
Height , h (cm)
Frequency, f
0<ℎ≤10 2
10<ℎ≤20 8
20<ℎ≤30 9
30<ℎ≤40 7
40 < ℎ ≤ 50 4
Mid-point, 𝒙
𝒇×𝒙 5
2 x 5 = 10 15
8 x 15 = 120 25
9 x 25 = 225 35
7 x 35 = 245 45
4 x 45 = 180
Total frequency = 30
Total 𝑓×𝑥 = 780
= = 26cm
Estimated mean 26
Exam Qu2
Sunday, 18 November 2018
By Cang Tu
1st Slide

5. Exam Qu 2
Ans 2a
Ans 2b
2) The table shows some information about the heights (h cm) of 100 students
Find the class interval in which the median lies (1 mark, C)
Work out an estimate for the mean height of the students
(4 marks, C)
Height , h (cm)
Frequency
120<ℎ≤130 8
130<ℎ≤140 16
140<ℎ≤150 25
150<ℎ≤160 30
160 < ℎ ≤ 170 21
Mid-point, 𝒙
𝒇×𝒙
125
8 x 125 = 1000
135
16 x 135 = 2160
145
25 x 145 = 3625
155
30 x 155 = 4650
165
21 x 165 = 3465
Total frequency = 100
Total 𝑓×𝑥 = 14900
150 <ℎ ≤160
= = 149cm
Estimated mean
Sunday, 18 November 2018
By Cang Tu
1st Slide