6. | Answer any five of the following: | 2x5 | |
| (a) | If for two events A and B, P(A) = | | , P(B) = | | and P (A∪B) = | | then P (exactly one of A and | B occurs) is (i) | | (ii) | | (iii) | | (iv) | none of these | | | (0) |
| (b) | If for two events A and B, P(A) = | | , P(B/A) = | | then P(A – B) is | | | (0) |
| (c) | If for three mutually exclusive and exhaustive events A, B and C P(A) = | | , P(B) and P(B) = | | P(C) | then P(A) is (i) | | (ii) | | (iii) | | (iv) | None of these | | | (0) |
| (d) | The standard deviation of the probability distribution | | is | then P(A) is (i) | | (ii) | 0.2 | (iii) | 1 | (iv) | √ 0.3 | | | (0) |
| (e) | If for two variables x and y | 10 Σ i = 1 | (xi – x)2 = 20, | 10 Σ i = 1 | (yi – y)2 = 45, | 10 Σ i = 1 | (xi – x ) (yi – y ) = 27, | then the correlation coefficient between x and y is (i) | 0.9 | (ii) | 0.6 | (iii) | 1 | (iv) | | | | (0) |
| (f) | For a random variable X following Poisson distribution with mean 2 then P(X ≥ 1) is (i) | e–2 | (ii) | 3e–2 | (iii) | 1 – e–2 | (iv) | 1 – 3e–2 | | | (0) |
| (g) | If X be a standard normal variable with | 1.96 ∫ –1.96 | (2π)½ e–x2/2 dx = 0.95 then P(X > 1.96) is |
(i) | 0.025 | (ii) | 0.25 | (iii) | 0.05 | (iv) | 0.475 | | | (0) |
| (h) | Proportion of defective items in a large lot of items is p. Taking a random sample of 6 items from the lot and accepting the null hypothesis if the number of defectives in the sample being 5 or less, then the probability of type II error when p = 0.3 is (i) | 1 – 4.2(0.3)5 | (ii) | 1 – 0.3 (4.2)5 | (iii) | 4.2 – (0.3)5 | (iv) | None of these | | | (0) |
| (i) | If two simple random samples each of size 5 are drawn with and without replacement from a finite population of size 21 with variance 25, have standard errors of sample means s1 and s2 respectively, then s1/s2 is | | (0) |
| (j) | A simple random sample of size 100 has mean 10, population variance being 25 and 1.96 ∫ –1.96 | (2π)–½ e–x2/2 dx = 0.95 Then the 95% upper confidence limit for population mean is |
(i) | 9.02 | (ii) | 10.98 | (iii) | 9.05 | (iv) | 10.95 | | | (0) |
7. | (a) | The personnel department of a company has records which show the following analysis of its 200 engineers: Age (in years) | Qualification | Total | Graduate | Post–Graduate | Under 30 30–40 Over 40 | 90 20 40 | 10 30 10 | 100 50 50 |
If an engineer is selected at random find the probability that he is (i) a graduate; (ii) a post–graduate given that his age is over 40; and (iii) under 30 and a graduate. | 5 | (0) |
| (b) | A shopkeeper of some highly perishable type of fruit observes that the daily demand of this fruit in his locality has the following probability distribution: Daily demand (in dozen) Probability | : : | 6 0.1 | 7 0.4 | 8 0.3 | 9 0.2 |
He sells for Rs. 10 a dozen while be buys each dozen at Rs. 4. Unsold fruits at the end of the day are sold next day at Rs. 2 per dozen. Assuming he stocks the fruits in dozens, how many dozens should he stock so that his expected profit is maximum? | 5 | (0) |
8. | (a) | A committee of 4 persons is to be appointed from 3 officers of the production department, 4 officers from the purchase department, 2 officers of the sales department and 1 Chartered Accountant. Find the probability of forming the committee such that there must be (i) one from each category; (ii) at least one from the purchase department; and (iii) the chartered Accountant. | 5 | (0) |
| (b) | Fit a binomial distribution to the following data and find expected frequencies: x f | : : | 0 20 | 1 120 | 2 140 | 3 80 | 4 40 | Total 400 |
Where x = number of heads, f = number of times x heads occur in 400 times of 4 tosses of a coin. | 5 | (0) |
9. | (a) | Find the correlation coefficient between x and y, the value of x when y = 10 and the value of y when x = 100 from the regression lines 2y = x + 50 and 3y = 2x + 10. | 5 | (0) |
| (b) | If X be a Poisson variable such that P(X = 0) + P(X = 1) = 4P(X = 2), find the probability that (i) X is positive, (ii) X is atmost one. | 5 | (0) |
10. | (a) | A random sample of size 10, drawn from a normal population with variance 4, has mean 48. Test at 5% level of significance the hypothesis that the population mean is 50. It is given that | 1.96 ∫ –∞ | (2π)–½ e–t2/2 dt = 0.975. | | 5 | (0) |
| (b) | In an infantile paralysis epidemic, 500 persons contracted the disease. 200 received no serum treatment and of these 75 became paralysed. Of those who received serum treatment, 65 became paralysed. Was the serum treatment effective? [Given | χ2 0.01 | = 6.64 at df = 1] | | 5 | (0) |
11. | (a) | A population consists of 5 height 60, 61, 62, 64, 62 in feet. Drawing all possible samples without replacement of size 2 from the population find the sampling distribution of the sample mean. Also find mean of the sampling distribution. | 5 | (0) |
| (b) | Write short note on any one: | 5 | |
| | (i) | Normal distribution and its uses; | | (0) |
| | (ii) | Scatter diagram and its uses. | | (0) |