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Statistics

Short Answer Type

441. Which of the following arguments are correct and which are not correct ? Give reasons for your answer.

(i) If two coins are tossed simultaneously there are three possible outcomes—two heads, two tails or one of each. Therefore, for each of these outcomes, the probability is

1 third.

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442.

The table below shown the salaries of 280 persons:

Salary (In thousand) No. of Person

5-10 49

10-15 133

15-20 63

20-25 15

25-30 6

30-35 7

35-40 4

40-45 2

45-50 1

Calculate the median salary of the data.

Long Answer Type

443.
The mean of the following distribution is 18. Find the frequency f of the class 19-21.

Class 11-13 13-15 15-17 17-19 19-21 21-23 23-25

Frequency 3 6 9 13 f 5 4

${Σf}_{i} u_{i} = f - 8 we have h = 2; A = 18, N = 40 + f {Σf}_{i} u_{i} = f - 8 X = 18 ∴ Mean = A + h \{\frac{1}{N} {Σf}_{i} u_{i}\} 18 = 18 + 2 \{\frac{1}{40 + f} (f - 8)\} \frac{2 (f - 8)}{40 + f} = 0 f - 8 = 0 f = 8$

Class	Mid values x_i	Frequency f_i	d_i = x_i -18	$u_{i} = \frac{x_{i} - 18}{2}$	f_iu_i
11-13	12	3	-6	-3	9
13-15	14	6	-4	-2	-12
15-17	16	9	-2	-1	-9
17-19	18	13	0	0	0
19-21	20	f	2	1	f
21-23	22	5	4	2	10
23-25	24	4	6	3	12
		$Σ f_{i} = 40 + f$

444.

The following distribution gives the daily income of 50 workers of a factory:

Daily Income (In) 100-120 120-140 140-160 160-180 180-200

Number of workers 12 14 8 6 10