# Statistics Class 11 NCERT Solutions

## In this pdf file you can see answers of following Questions

### EXERCISE 15.1

Find the mean deviation about the mean for the data in Exercises 1 and 2.

Question 1. 4, 7, 8, 9, 10, 12, 13, 17

Question 2. 38, 70, 48, 40, 42, 55, 63, 46, 54, 44

Find the mean deviation about the median for the data in Exercises 3 and 4.

Question 3. 13, 17, 16, 14, 11, 13, 10, 16, 11, 18, 12, 17

Question 4. 36, 72, 46, 42, 60, 45, 53, 46, 51, 49

Find the mean deviation about the mean for the data in Exercises 5 and 6.

Question 5. xi 5 10 15 20 25 f i 7 4 6 3 5

Question 6. xi 10 30 50 70 90 f i 4 24 28 16 8

Find the mean deviation about the median for the data in Exercises 7 and 8.

Question 7. xi 5 7 9 10 12 15 f i 8 6 2 2 2 6

Question 8. xi 15 21 27 30 35 f i 3 5 6 7 8

Find the mean deviation about the mean for the data in Exercises 9 and 10.

Question 9. Income 0-100 100-200 200-300 300-400 400-500 500-600 600-700 700-800
per day Number 4 8 9 10 7 5 4 3
of persons

Question 10. Height 95-105 105-115 115-125 125-135 135-145 145-155
in cms
Number of 9 13 26 30 12 10
boys

Question 11. Find the mean deviation about median for the following data :
Marks 0-10 10-20 20-30 30-40 40-50 50-60
Number of 6 8 14 16 4 2
Girls

Question 12. Calculate the mean deviation about median age for the age distribution of 100 persons given below:
Age 16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55
Number 5 6 12 14 26 12 16 9

### EXERCISE 15.2

Find the mean and variance for each of the data in Exercies 1 to 5.

Question 1. 6, 7, 10, 12, 13, 4, 8, 12

Question 2. First n natural numbers

Question 3. First 10 multiples of 3

Question 4. xi 6 10 14 18 24 28 30 fi 2 4 7 12 8 4 3

Question 5. xi 92 93 97 98 102 104 109 f i 3 2 3 2 6 3 3

Question 6. Find the mean and standard deviation using short-cut method.
xi 60 61 62 63 64 65 66 67 68
f i 2 1 12 29 25 12 10 4 5

Find the mean and variance for the following frequency distributions in Exercises 7 and 8.

Question 7. Classes 0-30 30-60 60-90 90-120 120-150 150-180 180-210
Frequencies 2 3 5 10 3 5 2

Question 8. Classes 0-10 10-20 20-30 30-40 40-50
Frequencies 5 8 15 16 6

Question 9. Find the mean, variance and standard deviation using short-cut method
Height 70-75 75-80 80-85 85-90 90-95 95-100 100-105105-110 110-115
in cms No. of 3 4 7 7 15 9 6 6 3
children

Question 10. The diameters of circles (in mm) drawn in a design are given below:
Diameters 33-36 37-40 41-44 45-48 49-52 No. of circles 15 17 21 22 25 Calculate the standard deviation and mean diameter of the circles.[ Hint First make the data continuous by making the classes as 32.5-36.5, 36.5-40.5, 40.5-44.5, 44.5 - 48.5, 48.5 - 52.5 and then proceed.]

### EXERCISE 15.3

Question 1. From the data given below state which group is more variable, A or B?
Marks 10-20 20-30 30-40 40-50 50-60 60-70 70-80
Group A 9 17 32 33 40 10 9
Group B 10 20 30 25 43 15 7

Question 2. From the prices of shares X and Y below, find out which is more stable in value:
X 35 54 52 53 56 58 52 50 51 49
Y 108 107 105 105 106 107 104 103 104 101

Question 3. An analysis of monthly wages paid to workers in two firms A and B, belonging to the same industry, gives the following results: Firm A Firm B No. of wage earners 586 648 Mean of monthly wages Rs 5253 Rs 5253 Variance of the distribution 100 121 of wages
(i) Which firm A or B pays larger amount as monthly wages?
(ii) Which firm, A or B, shows greater variability in individual wages?

Question 4. The following is the record of goals scored by team A in a football session:
No. of goals scored 0 1 2 3 4
No. of matches 1 9 7 5 3
For the team B, mean number of goals scored per match was 2 with a standard deviation 1.25 goals. Find which team may be considered more consistent?

Question 5. The sum and sum of squares corresponding to length x (in cm) and weight y (in gm) of 50 plant products are given below: 50 1 i 212 i x = Σ = , 50 2 1 i 902 8 i x . = Σ = , 50 1 i 261 i y = Σ = , 50 2 1 i 1457 6 i y . = Σ = Which is more varying, the length or weight?

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