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Question 15

Consider the given data with frequency distribution

$$x_i$$38111054
$$f_i$$523244

Match each entry in List-I to the correct entries in List-II.

List-IList-II
(P)The mean of the above data is(1)2.5
(Q)The median of the above data is(2)5
(R)The mean deviation about the mean of the above data is(3)6
(S)The mean deviation about the median of the above data is(4)2.7
(5)2.4

The correct option is:

The six distinct observations are $$x_i=3,\,4,\,5,\,8,\,10,\,11$$ with corresponding frequencies $$f_i=5,\,4,\,4,\,2,\,2,\,3$$.

Total number of observations
$$N=\sum f_i = 5+4+4+2+2+3 = 20$$

Case P : Mean
The mean is $$\bar x = \dfrac{\sum f_i x_i}{N}$$.
$$\sum f_i x_i = 3\!(5)+4\!(4)+5\!(4)+8\!(2)+10\!(2)+11\!(3)=15+16+20+16+20+33=120$$
$$\bar x=\dfrac{120}{20}=6$$
So $$\bar x=6$$, which is entry (3).

Case Q : Median
The cumulative frequencies are $$5,\,9,\,13,\,15,\,17,\,20$$.
For $$N=20$$ (even), the median is the average of the $$10^{\text{th}}$$ and $$11^{\text{th}}$$ items.
Both the $$10^{\text{th}}$$ and $$11^{\text{th}}$$ items lie in the class $$x=5$$ (cumulative frequency just exceeds 9).
Hence $$\text{Median}=5$$, which is entry (2).

Case R : Mean deviation about the mean
Mean deviation about the mean is $$\dfrac{\sum f_i \lvert x_i-\bar x\rvert}{N}$$.
$$\begin{aligned} \sum f_i \lvert x_i-\bar x\rvert &= 5\lvert3-6\rvert +4\lvert4-6\rvert +4\lvert5-6\rvert +2\lvert8-6\rvert \\ &\quad +2\lvert10-6\rvert +3\lvert11-6\rvert \\ &=5(3)+4(2)+4(1)+2(2)+2(4)+3(5)\\ &=15+8+4+4+8+15=54 \end{aligned}$$
$$\text{M.D. about mean}= \dfrac{54}{20}=2.7$$, which is entry (4).

Case S : Mean deviation about the median
Mean deviation about the median is $$\dfrac{\sum f_i \lvert x_i-\text{Median}\rvert}{N}$$.
$$\begin{aligned} \sum f_i \lvert x_i-5\rvert &= 5\lvert3-5\rvert +4\lvert4-5\rvert +4\lvert5-5\rvert +2\lvert8-5\rvert \\ &\quad +2\lvert10-5\rvert +3\lvert11-5\rvert \\ &=5(2)+4(1)+4(0)+2(3)+2(5)+3(6)\\ &=10+4+0+6+10+18=48 \end{aligned}$$
$$\text{M.D. about median}= \dfrac{48}{20}=2.4$$, which is entry (5).

Thus the correct matching is
$$P\rightarrow(3),\;Q\rightarrow(2),\;R\rightarrow(4),\;S\rightarrow(5).$$
Therefore, the correct option is Option A.

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