Question

find the mean if the given data marks: 20 40 60 80 10 number of students 6 10 10 9 5​

Answer 1

Answer:

Class Interval

Frequency

10-19

20-29

30-39

40-49

50-59

60-69

70-79

6

4

10

9

11

8

2

Change the class interval into continuous data.

Class Interval

Frequency

Midpoint x

i

∣x

i

−M∣

f

i

(x

i

−M)

9.5-19.5

19.5-29.5

29.5-39.5

39.5-49.5

49.5-59.5

59.5-69.5

69.5-79.5

6

4

10

9

11

8

2

14.5

24.5

34.5

44.5

54.5

64.5

74.5

37.9

39.9

33.9

34.9

32.9

35.9

30.1

226.8

159.6

339

314.1

361.9

287.2

60.2

∑f=50

∑f

i

(x

i

−M)=1748.8

x

=

50

2195

=43.9

Therefore, Mean deviation about Mean,

∑f

∑f

i

(x

i

−M)

=

50

1748.8

=34.976.