Statistics

If the mean and the variance of 6, 4, a, 8, b, 12, 10, 13 are 9 and 9.25 respectively, then a + b + ab is equal to :

1. 103
2. 106
3. 100
4. 105

Let x1, x2, , x10 be ten observations such that i=110(xi - 2) = 30, i=110(xi - )2 = 98, > 2, and their variance is 45. If and 2 are respectively the mean and the variance of 2(x1 - 1) + 4 , 2(x2 - 1) + 4 , , 2(x10 - 1) + 4 , then 2 is equal to :

1. 100
2. 90
3. 120
4. 110

For a statistical data x1, x2, , x10 of 10 values, a student obtained the mean as 5.5 and i=110xi2=371. He later found that he had noted two values in the data incorrectly as 4 and 5, instead of the correct values 6 and 8, respectively. The variance of the corrected data is

1. 5
2. 7
3. 9
4. 4

Marks obtains by all the students of class 12 are presented in a freqency distribution with classes of equal width. Let the median of this grouped data be 14 with median class interval 12-18 and median class frequency 12. If the number of students whose marks are less than 12 is 18 , then the total number of students is :

1. 52
2. 44
3. 40
4. 48

The variance of the numbers 8, 21, 34, 47, , 320 is .

The frequency distribution of the age of students in a class of 40 students is given below. [figure] If the mean deviation about the median is 1.25, then 4x + 5y is equal to :

1. 43
2. 46
3. 44
4. 47

If the variance of the frequency distribution array|c|c|c|c|c|c|c| x & c & 2c & 3c & 4c & 5c & 6c \ f & 2 & 1 & 1 & 1 & 1 & 1 \ array is 160, then the value of c N is

1. 5
2. 8
3. 6
4. 7

Let a, b, c N and a < b < c. Let the mean, the mean deviation about the mean and the variance of the 5 observations 9, 25, a, b, c be 18, 4 and 1365, respectively. Then 2a + b - c is equal to

The mean and standard deviation of 20 observations are found to be 10 and 2, respectively. On rechecking, it was found that an observation by mistake was taken 8 instead of 12. The correct standard deviation is

1. 1.94
2. 3.96
3. 3.86
4. 1.8

Let , R. Let the mean and the variance of 6 observations -3, 4, 7,-6, , be 2 and 23, respectively. The mean deviation about the mean of these 6 observations is :

1. 163
2. 113
3. 143
4. 133