(N/A) The given cumulative frequency distributions of less than type are:
| Weight (in kg) (upper class limits) | Number of students (cumulative frequency) |
|---|
| Less than $38$ | $0$ |
| Less than $40$ | $3$ |
| Less than $42$ | $5$ |
| Less than $44$ | $9$ |
| Less than $46$ | $14$ |
| Less than $48$ | $28$ |
| Less than $50$ | $32$ |
| Less than $52$ | $35$ |
Taking upper class limits on the $x$-axis and their respective cumulative frequencies on the $y$-axis,the ogive is drawn as shown in the figure.
Here,$n = 35$.
So,$\frac{n}{2} = 17.5$.
Mark the point $A$ on the curve whose ordinate is $17.5$. The $x$-coordinate corresponding to this point is $46.5$. Therefore,the median of this data is $46.5$.
To verify using the formula,we first determine the class intervals and their frequencies:
| Weight (in kg) | Frequency $(f)$ | Cumulative frequency $(cf)$ |
|---|
| $38-40$ | $3-0=3$ | $3$ |
| $40-42$ | $5-3=2$ | $5$ |
| $42-44$ | $9-5=4$ | $9$ |
| $44-46$ | $14-9=5$ | $14$ |
| $46-48$ | $28-14=14$ | $28$ |
| $48-50$ | $32-28=4$ | $32$ |
| $50-52$ | $35-32=3$ | $35$ |
The cumulative frequency just greater than $\frac{n}{2} = 17.5$ is $28$,which belongs to the class interval $46-48$.
Median class $= 46-48$.
Lower class limit $(l) = 46$.
Frequency $(f) = 14$.
Cumulative frequency of the class preceding the median class $(cf) = 14$.
Class size $(h) = 2$.
Using the median formula:
$\text{Median} = l + \left( \frac{\frac{n}{2} - cf}{f} \right) \times h$
$= 46 + \left( \frac{17.5 - 14}{14} \right) \times 2$
$= 46 + \left( \frac{3.5}{14} \right) \times 2$
$= 46 + \frac{7}{14} = 46 + 0.5 = 46.5$.
The result is verified.