AP Stat 46-60

49. Staff members of a high school newspaper want to obtain an estimate of the average number of years teachers in the state have been teaching. At an educational conference attended by many teachers in the state, the staff members randomly selected 50 conference attendees and asked the attendees how long they have been teaching. Which of the following describes the sample and the population to which it would be most reasonable for the staff members to generalize the results? a) the sample is the 50 conference attendees and the population is all teachers in the state. b) the sample is the 50 conference attendees and the population is all the conference attendees. c) the sample is all conference attendees and the population is all teachers in the state. d) the sample is all conference attendees and the population is the 50 conference attendees. e) the sample is the average number of years that all conference attendees have taught, and the population is all conference attendees.

B. The sample is the 50 conference attendees, and the population is all the conference attendees.

47. Which of the following are true statements? I. The area under a norm al curve is always equal to 1, no matter what the mean and standard deviation are. II. The smaller the standard deviation of a normal curve, the higher and narrower the graph. III. Normal curves with different means are centered around different numbers. a) I and II b) I and III c) II and III d) I, II, and III e) none of the above gives the complete set of true responses

D. I, II, and III

46. Which of the following are true? I. Two events are mutually exclusive if they can't occur at the same time. II. Two events are independent if they have the same probability. III. An event and its complement have probabilities that always add to 1. a) I only b) II only c) III only d) I and II only e) I and III only

E. I and III only

48. A national consumer magazine reported the following correlations. -The correlation between car weight and car reliability is -0.30. -The correlation between car weight and annual maintenance cost is 0.20. Which of the following statements are true? I. Heavier cars tend to be less reliable. II. Heavier cars tend to cost more to maintain. III. Car weight is related more strongly to reliability than to maintenance cost. a) I only b) II only c) III only d) I and II e) I, II, and III

E. I, II, and III

58. A population of bolts has a mean thickness of 20 millimeters, with a population standard deviation of 0.01 millimeters.- Give, in millimeters, a minimum and maximum thickness that will include 95% of the population of bolts. a) 19.98 to 20.02 millimeters b) 19.99 to 20.01 millimeters c) 19.97 to 20.03 millimeters d) 19.8 to 20.2 millimeters e) These can't be accurately computed.

a) 19.98 to 20.02 millimeters

52. A study was conducted to evaluate the impact of taking a nutritional supplement on a person's reaction time. One hundred volunteers were placed into one of three groups according to their athletic ability:low, moderate, or high. Participants in each group were randomly assigned to take either the nutritional supplement or a placebo for six weeks. At the end of the six weeks, participants were given a coordination task. The reaction time in completing the task was recorded for each participant. The study compared the reaction times between those taking the supplement and those taking the placebo within each athletic ability level. Which of the following is the best description of the study? a) a randomized block design b) a completely randomized design c) a matched- pairs design d) a randomized observational study e) a stratified observational study

a)a randomized block design

56. Molly earned a score of 940 on a national achievement test. The mean test score was 850 with a standard deviation of 100. What proportion of students had a higher score than Molly? (Assume that test scores are normally distributed) a)0.10 b)0.18 c)0.50 d)0.82 e)0.90

b) 0.18

60. Given two events, E and F, such that P(E)=.340, P(F)=.450, and P(EUF)=.637, then the two events are: a) independent and mutually exclusive b) independent, but not mutually exclusive c) mutually exclusive, but not independent d) neither independent nor mutually exclusive e) there is not enough information to answer the question

b) independent, but not mutually exclusive

54. A residual: a) is the amount of variation explained by the least-squares regression lone of y on x. b) is how much an observed y-value differs from a predicted y-value. c) predicts how well x explains y. d) is the total variation of the data points. e) should be smaller than the mean of y.

b) is how much an observed y-value differs from a predicted y-value.

51. It is estimated that 20 percent of all drivers do not signal when changing lanes. In a random sample of four drivers, what is probability that at least one doesn't signal when changing lanes? a) 1-(.2)^4 b) 1-(.8)^4 c) 4(.2)(.8)^3 d) 4(.2)^3(.8) e) 4(.2)^3(.8)+6(.2)^2(.8)^2+4(.2)(.8)^3+(.8)^4

b)1-(.8)^4

59. The SAT math scores for applicants to a particular engineering school are normally distributed with a mean of 680 and a standard deviation of 35. Suppose that only applicants with scores above 700 are considered for admission. What percentage of the applicants considered have scores below 750? a) 2.3 percent b) 26.1 percent c) 71.6 percent d) 92.0 percent e) 97.7 percent

b)26.1 percent

50. Suppose P(X)=.25 and P(Y)=.40. If P(XIY)=.20, what is P(YIX)? a) .10 b) .125 c) .32 d) .45 e) .50

c) .32

55. The number of tickets purchased by a customer for the Ice Hogs game at BMO Harris Bank center can be considered a random variable. The table below show the relative frequency distribution for the number of tickets purchased by a customer. (chart on test) Suppose each ticket for the game cost $12. Based on the distribution shown, what is the mean cost per customer for the game? a)$2.45 b)$2.75 c)$24.50 d)$29.40 e)$36.00

d) $29.40

53. The average noise level in a bar is 36 decibels with a standard deviation of 5 decibels. Assuming a normal distribution, what is the probability the noise level is between 30 and 40 decibels? a) 0.327 b) 0.337 c) 0.381 d) 0.673 e) 0.683

d) 0.673

57. A population of bolts has a mean thickness of 20 millimeters, with a population standard deviation of 0.01 millimeters.- Give, in millimeters, a minimum and maximum thickness that includes 68% of the population of bolts. a) 20.00 to 20.02 millimeters b) 19.00 to 21.00 millimeters c) 19.98 to 20.02 millimeters d) 19.99 to 20.01 millimeters e) 19.97 to 20.03 millimeters

d) 19.99 to 20.01 millimeters