The marks obtained by 7 students are 8,9,11 ,13,14,15,21.Find the variance and standard deviation of these marks.

2

(a)

Two plants A and B of a factory show results about the number of workers and wages paid to them.

	A	B
Number of workers	5000	6000
Average monthly wages	2500	2500
Variance of distribution of wages	81	100

Which plants A or B is the greater variability in individual wages?

2

(a)

Find the variance of the data 6,5,9,13,12,8 and 10.

2

(a)

Find the standard deviation of first 10 natural numbers

2

(a)

Find the mean deviation about the mean for the following data
36,72,46,60,45,42,53,49,51,46

2

(a)

Find the mean deviation about the median for the following data
34,66,44,30,38,50,42,51,40,60

2

(a)

Find the mean, variance and standard deviation of the following data: 62, 65, 57, 56, 69, 51, 62, 60

2

(a)

Find the mean, variance and standard deviation of the following data: 15, 22, 27, 14, 9, 9, 11, 21

2

(a)

Find the mean, variance and standard deviation of the following data:

xi	3.5	4.5	5.5	6.5	7.5	8.5	9.5
fi	3	7	22	60	85	32	8

2

(a)

The coefficient of variation of two distribution are 55% and 70% and their standard deviations are 20 and 18 respectively. What are their arithmetic means?

2

(a)

Suppose that samples balloons from two manufacturers A and B are tested by a trader for bursting pressure as follows;

Bursting pressure	Number of balloons manufactured by
	A	B
5-10	2	9
10-15	9	11
15-20	29	18
20-25	54	32
25-30	11	27
30-35	5	13

Which balloons have the highest average bursting pressure?

2

(a)

The following are some particulars of the distribution of weights of boys and girls in a class:

	Boys	Girls
Number	100	50
Mean Weight	60kg	45kg
Variance	9	4

Which of the distributions is more variable?

2

(a)

The variance of20observations is 5. If each observation is increased by 5, find the new variance.

2

(a)

The mean and S.D. of 100 students of a class in the subjects English, Maths and Science are given below

Subject	English	Maths	Science
Mean	51	60	45
S.D	12	15	9

Which of the three subjects is more consistent and which is more variable?

2

(a)

Find the variance of the following data:

Classes	0-10	10-20	20-30	30-40	40-50
Frequencies	15	20	22	27	6

2

(a)