Question

1.You plan to randomly select 10 students from your campus and ask them how many minutes they exercised in the past seven days. The distribution of values taken by the average exercising time in all possible samples of size 10 is the (a) probability distribution of exercising times. (b) sampling distribution of average exercising times. (c) variance of the exercising time values. (d) population parameter. Use the following to answer Questions 2-4. A researcher cross-classified 386 trout into groups based on their species (all were in genus Salmo) and gender. The results follow. Species Female Male Brown 68 56 Flathead 91 40 Ohrid 5 6 Sevan 61 59 A trout is to be selected at random. 2. The probability that the selected trout is a Brown trout is a. 0.1451. b. 0.1762. c. 0.3212. d. 0.6788. 3. The probability that the selected trout is a male Brown trout is a. 0.1451. b. 0.1762. c. 0.3212. d. 0.6788. 4. Given that the selected trout is male, the conditional probability that it is a Sevan trout is a. 0.0776. b. 0.1717. c. 0.3665. d. 0.4516. 5. Event A occurs with probability 0.3, and event B occurs with probability 0.4. If A and B are independent, we may conclude that a. P(A and B) = 0.12. b. P(A|B) = 0.3. c. P(B|A) = 0.4. d. All of the above Use the following to answer Questions 6 and 7. A recent nationwide study of myopia (nearsightedness) found that 38.1% of American adults ages 18 to 24 suffer from myopia. Consider two young adults between the ages of 18 and 24, chosen randomly and independently. 6. The probability that both individuals suffer from myopia is a. 0.145. b. 0.381. c. 0.617. d. 0.762. 7. The probability that neither of them suffer from myopia is a. 0.238. b. 0.383. c. 0.619 d. 0.855. Use this information for Questions 8 and 9. Birth weights at a local hospital have a Normal distribution with a mean of 110 ounces and a standard deviation of 15 ounces. 8. The proportion of infants with birth weights above 125 ounces is a. 0.500. b. 0.159. c. 0.341. d. 0.841. 9. The proportion of infants with birth weights between 125 ounces and 140 ounces is a. 0.819. b. 0.636. c. 0.477. d. 0.136. 10. The sampling distribution of a statistic is a. the probability that we obtain the statistic in repeated random samples. b. the mechanism that determines whether randomization was effective. c. the distribution of values taken by a statistic in all possible samples of the same size from the same population. d. the extent to which the sample results differ systematically from the truth. 11. The central limit theorem says that, when a simple random sample of size n is drawn from any population with mean  and standard deviation , then when n is sufficiently large a. the standard deviation of the sample mean is 2 / n. b. the distribution of the population is exactly Normal. c. the distribution of the sample mean is approximately Normal. d. the distribution of the sample mean is exactly Normal.

Answer 1

	female	MALE
brown	68	56	124
flathead	91	40	131
ohrid	5	6	11
sevan	61	59	120
	225	161	386

2. The probability that the selected trout is a Brown trout is a.

= 124/386

= 0.3212

3. The probability that the selected trout is a male Brown trout is

=56/386

= 0.1451

4. Given that the selected trout is male, the conditional probability that it is a Sevan trout is a

=59/161

=0.3665

5)

P(A ) = 0.3

P(B) = 0.4

P( A and B) = P(A) P(B)   if A and B are independent

= 0.12

P(A|B) = P(A) = 0.3

P(B|A) = P(B) = 0.4

hence D) all of the above is correct

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