NCERT Solutions class-11 Maths Exercise 15.1

Exercise 15.1

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

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

Ans. Mean of the given data

Mean deviation about mean = = = 3

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

Ans. Mean of the given data

Mean deviation about mean =

= = 8.4

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

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

Ans. Arranging the data in ascending order, 10, 11, 12, 13, 13, 14, 16, 11, 18, 12, 17

Here, (even number)

Mean =

= = 13.5

Mean deviation about median =

= = 2.33

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

Ans. Arranging the data in ascending order, 36, 42, 45, 46, 46, 49, 51, 53, 60, 72

Here, (even number)

Mean = = = 47.5

Mean deviation about median =

= = 7

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

5.

Ans.

Mean

= = 14

Mean deviation about mean =

= = 6.32

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6.

Ans.

Mean

= = 50

Mean deviation about mean =

= = 16

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

7.

Ans.

Here, = 13 and = 7

Median = 7

Mean deviation about median =

= = 3.23

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8.

Ans.

Here, = 14.5 and = 21

Median = 30

Mean deviation about median =

= = 5.1

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

9.

Ans.

Mean

= = 358

Mean deviation about mean =

= = 157.92

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10.

Ans.

Mean

= = 125.3

Mean deviation about mean =

= = 11.28

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11. Find the mean deviation about median for the following data:

Ans.

Here, = 25

Median class = 20 – 30

Median =

= 20 + 7.86 = 27.86

Mean deviation about median =

= = 10.37

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12. Calculate the mean deviation about median age for the age distribution of 100 persons given below:

Ans.

Here, = 50

Median class = 35.5 – 40.5

Median =

= 35.5 + 2.5 = 38

Mean deviation about median =

= = 7.35