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Question
From the following frequency, prepare the ‘more than’ ogive.
| Score | Number of candidates |
| 400 – 450 | 20 |
| 450 – 500 | 35 |
| 500 – 550 | 40 |
| 550 – 600 | 32 |
| 600 – 650 | 24 |
| 650 – 700 | 27 |
| 700 – 750 | 18 |
| 750 – 800 | 34 |
| Total | 230 |
Also, find the median.
Solution
From the given table, we may prepare than ‘more than’ frequency table as shown below:
| Score | Number of candidates |
| More than 750 | 34 |
| More than 700 | 52 |
| More than 650 | 79 |
| More than 600 | 103 |
| More than 550 | 135 |
| More than 500 | 175 |
| More than 450 | 210 |
| More than 400 | 230 |
We plot the points A(750, 34), B(700,52),
C(650, 79), D(600, 103), E(550, 135), F(500, 175),
G(450, 210) and H(400, 230).
Join AB, BC, CD, DE, EF, FG, GH and HA with
a free hand to get the curve representing the
‘more than type’ series.
Here, N = 230
⇒ `N/2 = 115`
From P (0, 115), draw PQ meeting the curve at Q. Draw QM meeting at M.
Clearly, OM = 590 units
Hence, median = 590 units.
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