51.

A data set of n observations has mean 2M, while another data set of 2n observations has mean M. What is the mean of the combined data sets ?

• M

• $\frac{3\mathrm{M}}{2}$

• $\frac{2\mathrm{M}}{3}$

• $\frac{4\mathrm{M}}{3}$

The sum of deviations of n number of observations measured from 2.5 is 50. The sum of deviations of the same set of observations measured from 3.5 is - 50. What is the value of n ?

• 50

• 60

• 80

• 100

What is the standard deviation of the observations

$- \sqrt{6}, - \sqrt{5}, - \sqrt{4}, - 1, 1, \sqrt{4}, \sqrt{5}, \sqrt{6} ?$

• $\sqrt{2}$

• 2

• $2\sqrt{2}$

• 4

Read the following information and answer the three items that follow :

What is the mean of marks in Physics ?

• 38.4

• 39.4

• 40.9

• 41.6

Read the following information and answer the three items that follow :

Consider the following statements:

1. Modal value of the marks in Physics lies in the interval 30 - 40.
2. Median of the marks in Physics is less than that of marks in Mathematics.

Which of the above statements is/are correct ?

• 1 only

• 2 only

• Both 1 and 2 

• Neither 1 nor 2

Read the following information and answer the three items that follow :

The difference between number of students under Physics and Mathematics is largest for the interval

• 20- 30

• 30 – 40

• 40 - 50

• 50 - 60