6. | Attempt any five of the following Choose the correct alternative stating proper reason: | 2x5=10 | |
| (a) | If A and B be two independent events such that P(A) = 0.4, P(A ∪ B) = 0.7 then the value of P(B) is | | (0) |
| (b) | If A, B and C be mutually exclusive and exhaustive events such that 1/3 P(C) = ½ P(A) = P(B) then the value of P(B) is | | (0) |
| (c) | If P(A) = | | , P(B) = | | and P(A ∪ B) = | | , then P(A/B) is |
(i) | | (ii) | | (iii) | | (iv) | None of these | | | (0) |
| (d) | If 6 fair coins are tossed simultaneously, then the probability of getting at least 4 heads is (i) | | (ii) | | (iii) | | (iv) | None of these | | | (0) |
| (e) | For the following probability distribution x : | 1 | 2 | 3 | p(x) : | ½ | 1/3 | 1/6 | the variance is | | (0) |
| (f) | If the distribution of a random variable X is normal with mean 0 and variace 1 with P(0 ≤ X ≤ 1) = 0.3413, then P(| X | > 1) is (i) | 0.6587, | (ii) | 0.3413, | (iii) | 0.3174, | (iv) | 0.6826. | | | (0) |
| (g) | If the correlation of a coefficient between x and y is 0.4, then the correlation coefficient between −3x and +5y is (i) | 0.4, | (ii) | −0.4, | (iii) | 0.3, | (iv) | –0.5. | | | (0) |
| (h) | If a random sample of size 5 is drawn without replacement from a finite population of 41 units with σ = 10, then the SE of sample mean is (i) | √2 | (ii) | 2√2 | (iii) | 3√2 | (iv) | None of these. | | | (0) |
| (i) | A random sample of size 100 has mean 15, the population variance being 25, then the 95% confidence interval for the population mean is (i) | (13.71, 16.29), | (ii) | (14.02, 15.98), | (iii) | (13.71, 14.12), | (iv) | (14.16, 16.31). | | | (0) |
| (j) | To test the null hypothesis H0: μ = 0 against H1; μ ≠ 0, 10 independent sample observations are drawn from a normal population with mean μ and unknown variance σ2. If the sample mean and variance are 6 and 4 respectively, the value of the appropriate test statistic is (i) | 6, | (ii) | 4, | (iii) | 10√3 | (iv) | 9. | | | (0) |
7. | (a) | A purse contains 4 nickel coins and 9 copper coins, while another purse contains 6 nickel and 7 copper coins. A purse is chosen at random and a coin is drawn at random from it. What is the probability that it is a nickel coin? | 5 | (0) |
| (b) | A problem is given to 5 students and their chances of solving it are ½, 1/3, ¼, 1/5 and 1/6. What is the probability that the problem will be solved? | 5 | (0) |
8. | (a) | A random variable X is binomially distributed with mean 4 and s.d. = √2.4. Find the probability that more than half the trials are successes. | 5 | (0) |
| (b) | A book contains 100 misprints distributed at random throughout its 100 pages. What is the probability that a page observed at random contains at least three misprints? [Given e = 2.718]. | 5 | (0) |
9. | (a) | Calculate the coefficient of correlation for the following data; x y | : : | 1 9 | 2 8 | 3 10 | 4 12 | 5 11 | 6 13 | 7 14 | 8 16 | 9 15 | | 5 | (0) |
| (b) | The regression lines of two correlated variables x and y are 5x − 6y + 90 = 0 and 15x − 8y − 130 = 0. Identify the regression lines x on y and y on x. Find the means and the correlation coefficient of the variables. | 5 | (0) |
10. | (a) | The coefficient of rank correlation of the marks obtained 10 students in two particular subjects was found to be 0.8. It was then detected that the difference in ranks in the two subjects obtained by one of the students was wrongly taken to be 7 in place of 9. What should be the correct rank correlation coefficient? | 5 | (0) |
| (b) | In 120 throws of a single die the following distribution of faces was observed: Face Frequency | : : | 1 30 | 2 25 | 3 18 | 4 10 | 5 22 | 6 15 |
Can you that the die is biased? [Given: the value of X2 at 5% level of significance for 5 df is 11.07] | 5 | (0) |
11. | (a) | Suppose a decision maker faced with three decision alternatives and two states of nature. Apply (1) maximin and (ii) minimax regret approach to the following pay–off table to recommend the decision. | State of nature | Act | S1 | S2 | A1 | 12 | 17 | A2 | 22 | 14 | A3 | 32 | 13 | | | (0) |
| (b) | In one sample of 8 observations, the sum of squares of the deviation of the sample values from the sample mean was 84.4 and in the other sample of 10 observations, it was 102.6. Test whether these differences are significant at 5% level, given that F0.05;(7,9) = 3.29 | 5 | (0) |