Find the mean, using direct method:

Class 25-35 35-45 45-55 55-65 65-75

Frequency 6 10 8 12 4

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Solution

Class

Frequency $(f_{i})$

Mid values $(x_{i})$

$(f_{i} \times x_{i})$

25-35

6

30

180

35-45

10

40

400

45-55

8

50

400

55-65

12

60

720

65-75

4

70

280

$\sum f_{i} = 40$

$\sum (f_{i} \times x_{i}) = 1980$

$∴ Mean, \bar{x} = \frac{\sum (f_{i} \times x_{i})}{\sum f_{i}} = \frac{1980}{40} =49 .5 ∴ \bar{x} = 49.5$

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Class	Frequency $(f_{i})$	Mid values $(x_{i})$	*$(f_{i} \times x_{i})$*
25-35	6	30	180
35-45	10	40	400
45-55	8	50	400
55-65	12	60	720
65-75	4	70	280
	$\sum f_{i} = 40$		$\sum (f_{i} \times x_{i}) = 1980$

Find the mean, using direct method: Class 25-35 35-45 45-55 55-65 65-75 Frequency 6 10 8 12 4

Find the mean, using direct method:

Class 25-35 35-45 45-55 55-65 65-75

Frequency 6 10 8 12 4