Q 11 :

The middle most observation of every data arranged in order is called:

  • Mode

     

  • Median

     

  • Mean

     

  • Deviation

     

(2)

The middle most observation of every data arranged in order is called median.

 



Q 12 :

The median of a given frequency distribution is found graphically with the help of:

  • Frequency curve

     

  • Bar graph
     

  • Histogram

     

  • An ogive

     

(4)

An ogive is a plot of the cumulative frequencies of a frequency distribution.
When the cumulative frequencies of class-intervals are plotted against upper or lower limits of class intervals, the graph obtained by joining the points by free hand forming smooth curve is called the cumulative frequency curve or ogive.
Ogive graphs are used to find the median of the given set of data.



Q 13 :

The median of the following observations given in order 16, 18, 20, 24 − x, 22 + 2x, 28, 30, 32 is 24. The value of x is:

  • 5

     

  • 4

     

  • 2

     

  • 1

     

(3)

Given, median of the data 16, 18, 20, 24 − x, 22 + 2x, 28, 30, 32 is 24.

Here, n=8(Even)Median=n2th observation +n2+1th observation224=4th observation+5th observation248=(24-x)+(22+2x)48=46+xx=2Hence, the value of x is 2.



Q 14 :

The mean and median of  a, b and c are 50 and 35, respectively, where a<b<c. If c - a = 55, then:

(i)  b - a = 10     (ii)  a + c = 115     (iii)  a = 20       (iv) b = 35

Choose the correct option from the following:

  • (i) and (iii)

     

  • (ii) and (iii)

     

  • (i) and (iv)

     

  • (ii) and (iv)

     

(4)

Since a < b < cMedian=bb=35Mean=a+b+c3=50a+b+c=150a+c=150-35=115(ii) is correct.Given, a + c = 115 c - a = 55  a=30  and  c=85b-a=35-30=5Option (d) is correct.



Q 15 :

The empirical relation between the mode, median and mean of a distribution is:

  • Mode = 3 Median − 2 Mean

     

  • Mode = 3 Mean − 2 Median
     

  • Mode = 2 Median − 3 Mean
     

  • Mode = 2 Mean − 3 Median

     

(1)

We know that the empirical relation is given by,

Mode = 3 Median − 2 Mean



Q 16 :

Using the empirical formula, the mode of a distribution whose mean is 8.32 and the median is 8.05, is equal to:

  • 7.51

     

  • 7.21

     

  • 7.01

     

  • 7.31

     

(1)

Given, mean = 8.32 and median = 8.05

∴ Mode = 3 × Median − 2 × Mean

= 3 × 8.05 − 2 × 8.32
= 24.15 − 16.64
= 7.51



Q 17 :

The times in seconds, taken by 150 athletes to run a 110 m hurdle race are tabulated below:

Class 13.8–14 14–14.2 14.2–14.4 14.4–14.6 14.6–14.8 14.8–15
Frequency 2 4 5 71 48 20

The number of athletes who completed the race in or equal to 14.6 seconds is:

  • 11

     

  • 71

     

  • 82

     

  • 130

     

(3)

We have,

Class Frequency Cumulative frequency
13.8–14 2 2
14–14.2 4 6
14.2–14.4 5 11
14.4–14.6 71 82
14.6–14.8 48 130
14.8–15 20 150

From the above cumulative frequency table, 82 athletes completed the race in or equal to 14.6 seconds.

 



Q 18 :

If the mode of the following data is K, then the value of K in the data set
9, 8, 6, 7, 1, 6, 10, 6, 7, K² − 12K + 42, 9, 7 and 13 is:

(i) 6  (ii) 9  (iii) 7  (iv) 13

Choose correct option from the following:

  • (iii) and (iv)

     

  • (i) and (iii)

     

  • Only (i)

     

  • (i) and (ii)

     

(2)

In the above dataset, value 6 and 7 have occurred most number of times, i.e., 3 times.

Also, mode = K.

So, either 6 or 7 would be the mode.

If K = 6,
K²  12K + 42 = 6²  12(6) + 42 = 6

If K = 7,
K²  12K + 42 = 7²  12(7) + 42 = 7

∴ K = 6 and K = 7

So, (i) and (iii) are correct.