MCQ
Look at the frequency distribution table given below:
Class interval
$35-45$ $45-55$ $55-65$ $65-75$
Frequency
$8$ $12$ $20$ $10$
The median of the above distribution is:
  • A
    $56.5$
  • $57.5$
  • C
    $58.5$
  • D
    $59$

Answer

Correct option: B.
$57.5$
Class intervalClass interval
FrequencyFrequency
Cumulative frequencyCumulative frequency
$35-45$ $8$ $8$
$45-55$ $12$ $20$
$55-65$ $20$ $40$
$65-75$ $10$ $50$
Here, $\text{N}=50$
$\Rightarrow\frac{\text{N}}{2}=25$
The cumulaove frequency just greater than $25$ is $40.$
Hence, median class is $55-65.$
Now, median $=\text{l}+\begin{Bmatrix}\text{h}\times\frac{\Big(\frac{\text{N}}{2}-\text{cf}\Big)}{\text{f}}\end{Bmatrix}$
$=55+\Big\{10\times\frac{(25-20)}{20}\Big\}$
$=55+2.5$
$=57.5$

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