Chapter 14: Statistics

Choose the correct answers :

Q1. The class-mark of the class 130 – 150 is :

(A) 130       (B) 135           (C)  140      (D)  145

Ans:  (C)  140 

 [Hints: The class mark =150+1302

=2802=140 ]

Q2. The marks obtained by 17 students in a mathematics test (out of 100) are given below :

91 , 82 , 100 , 100 , 96 , 65 , 82 , 76 , 79 , 90 , 46 , 64 , 72 , 68 , 66 , 48 , 49 .

The range of the data is :

(A) 46         (B) 54    (C) 90     (D) 100

Ans:   (B) 54  

[ We arrange the marks in ascending order as : 46 , 48 , 49 , 64 , 65 , 66 , 68 , 72 , 76 , 79 , 82 , 82 , 90 , 91 , 96 , 100 , 100

The range = 100 – 46 = 54 ]

Q3. The range of the data :

25 , 18 , 20 , 16 , 6 , 17 , 15 , 12 , 30 , 32 , 10 , 19 , 8 , 11 , 20 is :

(A) 10           (B)  15       (C)  18      (D) 26

Ans :  (D)  26

[ We arrange the marks in ascending order as : 6 , 8 , 10 , 11 , 12 , 15 , 16 , 17 , 18 , 19 , 20 , 20 , 25 , 30 , 32

The range = 32 – 6 = 26 ]

Q4. In a frequency distribution, the mid value of a class is 10 and the width of the class is 6 . The lower limit of the class is :

(A) 6          (B) 7       (C)  8       (D) 12

Ans:   (B)  7  .

  [ Let x and y be upper and lower limit respectively .

A/Q ,  10=x+y2 ⇒x+y=20……i

And   x-y=6……ii

 i+ii⇒x+y+x-y=20+6

 ⇒2x=26

 ⇒x=13

 i-ii⇒x+y-x-y=20-6

 ⇒x+y-x+y=14

 ⇒2y=14

⇒y=7  

Upper limit = 13  and Lower limit = 7 ]

Q5.  The width of each of five continuous classes in a frequency distribution is 5 and the lower class-limit of the lowest class is 10 . The upper class-limit of the highest class is :

(A) 15    (B) 25    (C) 35     (D) 40

Ans:  (C) 35 

[ Hints: The width of the class = 5

And  Lower class limit is 10

So , Upper class limit = 10 + 5 = 15

Now , The class interval are : 10 – 15  , 15 – 20 , 20 – 25 , 25 – 30  , 30 – 35 ]