MCQ
Statement $A ($Assertion$)$ : Consider the following frequency distribution:
Class interval $3-6$ $6-9$ $9-12$ $12-15$ $15-18$ $18-21$
Frequency $2$ $5$ $21$ $23$ $10$ $12$
The mode of the above data is $12.4 .$
Statement $R ($Reason$):$ The value of the variable which occurs most often is the mode.
  • A
    Both assertion $(A)$ and reason $(R)$ are true and reason $(R)$ is the correct explanation of assertion $(A)$.
  • Both assertion $(A)$ and reason $(R)$ are true and reason $(R)$ is not the correct explanation of assertion $(A).$
  • C
    Assertion $(A)$ is true but reason $(R)$ is false.
  • D
    Assertion $(A)$ is false but reason $(R)$ is true.

Answer

Correct option: B.
Both assertion $(A)$ and reason $(R)$ are true and reason $(R)$ is not the correct explanation of assertion $(A).$
Clearly, Reason is true.
The maximum frequency is $23$ and the modal class is $12-15.$
$\therefore l=12, f_1=23, f_0=21, f_2=10$ and $h=3$
$\therefore \text { Mode }=12+\left(\frac{23-21}{2 \times 23-21-10}\right) \times 3$
$=\left(12+3 \times \frac{2}{15}\right)$
$=12.4$
$\therefore$ Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Class Class marks $\left(x_i\right)$ Frequency $\left(f_i\right)$ $f_i x_i$
$1-3$ $2$ $12$ $24$
$3-5$ $4$ $22$ $88$
$5-7$ $6$ $27$ $165$
$7-9$ $8$ $19$ $152$
    $\Sigma f_i=80$ $\Sigma f_i x_i=426$
$\therefore$ Mean $=\frac{\sum f_i x_i}{\sum f_i}=\frac{426}{80}=5.325$

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