NDA 2016 Paper 2 | Statistics Question 8 | Mathematics

Consider the following statements in respect of class intervals of grouped frequency distribution.

I. Class-intervals need not be mutually exclusive.

II. Class-intervals should be exhaustive

III. Class-intervals need not be of equal width

Which of the above statements are correct?

I and II

II and III

I and III

I, II and III

NDA 2016 Paper 2

MCQ (Single Correct Answer)

+2.5

-0.83

Two variates, x and y are uncorrelated and have standard deviations $$\sigma$$_x and $$\sigma$$_y respectively. What is the correlation coefficient between x + y and x $$-$$ y ?

$${{{\sigma _x}{\sigma _y}} \over {\sigma _x^2 + \sigma _y^2}}$$

$${{{\sigma _x} + {\sigma _y}} \over {2{\sigma _x}{\sigma _y}}}$$

$${{\sigma _x^2 - \sigma _y^2} \over {\sigma _x^2 + \sigma _y^2}}$$

$${{{\sigma _y} - {\sigma _x}} \over {{\sigma _x}{\sigma _y}}}$$

NDA 2016 Paper 2

MCQ (Single Correct Answer)

+2.5

-0.83

If the covariance between x and y is 30, variance of x is 25 and variance of y is 144, then what is the correlation coefficient?

0.4

0.5

0.6

0.7

NDA 2016 Paper 2

MCQ (Single Correct Answer)

+2.5

-0.83

A random sample of 20 people is classified in the following table according to their ages.

Age	Frequency
15-25	2
25-35	4
35-45	6
45-55	5
55-65	3

What is the mean age of this group of people?

41.0

41.5

42.0

42.5

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