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Worked Example 4

The height of plants were measured during an experiment . the results are summarised in the table.

Height (h cm) Frequency

0 h 5 20

5 h 10 40

10 h 15 60

15 h 25 80

25 h 50 50

Total 250

  1. Draw up a cumulative frequency table for this distribution
  2. Determine which class interval contains the median height .

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Worked Example 4

Height (h cm) Frequency cumulative frequency

0 h 5 20 20

5 h 10 40 60

10 h 15 60 120

15 h 25 80 200

25 h 50 50 250

Total 250

Answer

a.

b.

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Worked Example 5

The examination marks of 300 students are summarised in the table .

  1. Draw a cumulative frequency table.
  2. Construct a cumulative frequency graph to show this data .
  3. Calculate an estimate for the median marks .

Marks frequency

1-10 3

11-20 7

21-30 13

31-40 29

41-50 44

51-60 65

61-70 70

71-80 49

81-90 14

90-100 6

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Worked Example 5

Answer

Marks frequency cumulative frequency

1-10 3 3

11-20 7 10

21-30 13 23

31-40 29 52

41-50 44 96

51-60 65 161

61-70 70 231

71-80 49 280

81-90 14 294

90-100 6 300

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Worked Example 5

Answer

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Worked Example 7

Twenty bean seeds were planted for a biology experiment . the heights of the plants were measured after three weeks and recorded as below.

Height (h cm) 0 h 3 3 h 6 6 h 9 9 h 12

Frequency 2 5 10 3

  1. Find an estimated for the mean height.
  2. Draw a cumulative frequency curve and find an estimate for the median height.

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Worked Example 7

Answer

Height (h cm) Mid- point frequency frequency x mid-point(fx) cumulativefrequency

0 h 3 1.5 2 3 2

3 h 6 4.5 5 22.5 7

6 h 9 7.5 10 75 17

9 h 12 10.5 3 31.5 20

Total 20 132

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Worked Example 7

Answer

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