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Question
Using a graph paper, drawn an Ogive for the following distribution which shows a record of the weight in kilograms of 200 students.
| Weight | Frequency |
| 40 - 45 | 5 |
| 45 - 50 | 17 |
| 50 - 55 | 22 |
| 55 - 60 | 45 |
| 60 - 65 | 51 |
| 65 - 70 | 31 |
| 70 - 75 | 20 |
| 75 - 80 | 9 |
Use your ogive to estimate the following:
(i) The percentage of students weighing 55kg or more.
(ii) The weight above which the heaviest 30% of the students fall.
(iii) The number of students who are:
(1) under-weight and
(2) over-weight, if 55·70 kg is considered as standard weight.
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Solution
| Weight | Frequency | c.f. |
| 40 - 45 | 5 | 5 |
| 45 - 50 | 17 | 22 |
| 50 - 55 | 22 | 44 |
| 55 - 60 | 45 | 89 |
| 60 - 65 | 51 | 140 |
| 65 - 70 | 31 | 171 |
| 70 - 75 | 20 | 191 |
| 75 - 80 | 9 | 200 |
(i) Number of student weighing 55 kg or more
= 200 - 44
= 156
∴ Percentage = `(156 xx 100)/(200)`
= 78%.
(ii) 30% of 200 = 60
∴ Heaviest w.t. (least)
= w.t. of 200 - 60
= 140th student
= 65 kg or more.
(iii) From ogive c.f. against 55.70 kg
= 45
∴ (1) number of under w.t. students
= 44
(2) number of over w.t. students
= 200 - 44
= 156.
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