Topic: Statistics (Test 1)



Topic: Statistics
Q.1
A batsman scores runs in 10 innings as 38,70,48,34,42,55,63,46,54 and 44 , then the mean score is
A. 494
B. 0.494
C. 4.94
D. 49.4
Answer : Option D
Explaination / Solution:

Mean (x) = 

               = 494/10

               = 49.4


Workspace
Report
Q.2
The mean of 5 observations is 4.4. If three observations are 1,2 and 6 and the difference of the other two is 5, then the other two observations are:
A. 5 and 9
B. 9 and 4
C. 4 and 8
D. 5 and 7
Answer : Option B
Explaination / Solution:

Let other two numbers be and 

Mean (x) = 4.4 = 

this gives ......(1) 

Also,        ........(2) 

Therefore from (1) and (2)

 x = 9 and  y = 4         


Workspace
Report
Q.3
Which one of the following average is most affected of extreme observations ?
A. G.M.
B. Mode
C. Median
D. A. M.
Answer : Option D
Explaination / Solution:

As A/M is calculated as the sum of all the observations divided by number of observations, so it is affected by if there is any change in the outliers

Workspace
Report
Q.4
S.D. of a data is 6. When each observation is increased by 1, then the S.D. of new data is
A. 7
B. 8
C. 5
D. 6
Answer : Option D
Explaination / Solution:


so it depends only on number of observations not on individual observations.


Workspace
Report
Q.5
If the coefficient of variation between x and y is 0.28, covariance between x and y is 7.6, and the variance of x is 9, then the S.D. of the y series is
A. 10.05
B. 9.8
C. 9.05
D. 10.1
Answer : Option C
Explaination / Solution:



Workspace
Report
Q.6
If the mean of the squares of first n natural numbers be 11, then n is equal to
A. - 13/ 2
B. 13
C. 5
D. 11
Answer : Option C
Explaination / Solution:



Workspace
Report
Q.7
If the two lines of regression are at right angles , then ρ(X,Y) is equal to
A. 1
B. -1
C. 0
D. 1 or - 1
Answer : Option C
Explaination / Solution:



Workspace
Report
Q.8
If mean = ( 3 median – mode ) x , then the value of x is
A. 1/2
B. 2
C. 3/2
D. 1
Answer : Option A
Explaination / Solution:

We know that, 3median = mode + 2 mean

so, mean= (3 median - mode)/2      ........(1)

comparing equation(1) with the given equation

therefore, x=1/2


Workspace
Report
Q.9
Which of the following is not a measure of dispersion ?
A. mean deviation
B. variance
C. range
D. mean
Answer : Option D
Explaination / Solution:

it is the measure of central tendency

Workspace
Report
Q.10
If the two lines of regression are 2x + y =7 and x + 2y = 7, then ρ(X,Y) is equal to
A. -1/4
B. - 1/ 2
C. 1/ 4
D. 1/ 2
Answer : Option B
Explaination / Solution:

let us assume that 2x + y =7 and x + 2y = 7 are lines of regression of y on x and x on y respectively

therefore, 

but sign of p will be same as  and 

hence, 


Workspace
Report