Ch13-15 Group QUIZ

1) Two friends, Ty and Skya, take a quiz every week 1) Two friends, Ty and Skya, take a quiz every week. From past experiences, it is known that both friends’ scores are approximately normally distributed, where Ty has a mean score of 90 with a standard deviation of 12, and Skya has a mean score of 85 with a standard deviation of 6. Assuming that their scores are independent, which of the following values is closest to the probability that Ty will have a lower score than Skya in a single quiz? A) 0.35 B) 0.39 C) 0.32 D) 0.20 E) None of these A

A survey asks a random sample of 100 OHS students if they support an increase in game tickets with additional revenue covering expense of academic tutors for students involved in extra-curricular activities. Let X denote the number in the sample that say they support the increase. Suppose 40% of all students at OHS support the increase. 2. The expected value (mean) of X is: a) 5% b) 0.40 c) 4 d) 40 e) 50

3) Mr. and Mrs. Garcia have each decided to provide extra credit points each week for the next 6 weeks. Suppose the amount of extra credit points provided in a week by Mr. Garcia is normally distributed with a mean of 5 points and a standard deviation of 1 point, and the amount of extra credit points provided in a week by Mrs. Garcia is normally distributed with a mean of 6 points and a standard deviation of 2 points. What is the expected number of weeks in a 6 week period that their combined extra credit will exceed 10 points?

A survey asks a random sample of 100 OHS students if they support an increase in game tickets with additional revenue covering expense of academic tutors for students involved in extra-curricular activities. Let X denote the number in the sample that say they support the increase. Suppose 40% of all students at OHS support the increase. 4. The standard deviation of X is: a) 24 b) 4.899 c) 16 d) 4 e) 0.058

5. Which one of these variables is a continuous random variable 5. Which one of these variables is a continuous random variable? a) The time is takes a randomly selected student to complete an exam. b) The number of tattoos a randomly selected person has. c) The number of women taller than 68 inches in a random sample of 5 women. d) The number of correct guesses on this part of the multiple choice test. e) None of these.

6. Which one of these variables is a discrete random variable 6. Which one of these variables is a discrete random variable? a) The time is takes a randomly selected student to complete a multiple choice exam. b) The amount of pizza eaten by a random sample of students. c) The number of women taller than 68 inches in a random sample of 5 women. d) The proportion of male birth rate in the world. e) None of these.

7. Suppose that for X = net amount won by a person playing a lottery game, the expected value is E(X) = -$0.50. What is the correct interpretation of this value? a) The most likely outcome of a single play is a net loss of 50 cents. b) A player will have a net loss of 50 cents every single time he/she plays this lottery game. c) Over a large number of plays the average outcome for plays is a net loss of 50 cents. d) A mistake must have been made because it’s impossible for an expected value to be negative. e) None of these

8. Pulse rates of adult men are approximately normal with a mean of 70 and a standard deviation of 8. Which choice correctly describes how to find the proportion of men that have a pulse rate greater than 78? a) Find the area to the left of z = -1 under a standard normal curve. b) Find the area to the left of z = 1 under a standard normal curve. c) Find the area between z = -1 and z = 1 under a standard normal curve. d) Find the area to the right of z = -1 under a standard normal curve. e) Find the area to the right of z = 1 under a standard normal curve.

500 people used a home test for HIV and then all underwent more conclusive hospital testing. The accuracy of the home test was evidenced in the following table: HIV Healthy Positive Test 35 25 Negative Test 5 435 9. What is the predictive value of the test? That is, what is the probability that a person tested has HIV and tests positive? a) 0.070 b) 0.130 c) 0.538 d) 0.95 e) 0.96

500 people used a home test for HIV and then all underwent more conclusive hospital testing. The accuracy of the home test was evidenced in the following table: HIV Healthy Positive Test 35 25 Negative Test 5 435 10. What is the specificity of the test? That is, what is the probability of testing negative given that the person does not have HIV? a) 0.125 b) 0.583 c) 0.870 d) 0.93 e) 0.950

500 people used a home test for HIV and then all underwent more conclusive hospital testing. The accuracy of the home test was evidenced in the following table: HIV Healthy Positive Test 35 25 Negative Test 5 435 11. What is the sensitivity of the test? That is, what is the probability that a person tested has HIV or tests negative? a) 0.070 b) 0.130 c) 0.95 d) 0.96 e) none of these

A new game of dice is being played with two dice on some college campuses. The dice are rolled one after the other. Instead of adding the numbers on each die, each player subtracts the number on the second die from the number on the first die. Let S = this difference. Note that for each die, µ = 3.5 and σ² ≈ 2.91. 12. Find P(S = -2). 1/9 or .111

13. At the start of a Scrabble game you turn over the 100 lettered tiles so that you cannot see them. There are four S’s and two blanks among the 100 tiles. If you pick one tile at random, what is the probability you will NOT get an S or a blank? a) 0.94 b) 0.68 c) 0.06 d) 0.92 e) None of these are the correct answer

14. A computer technician notes that 40% of computers fail because of the hard drive, 25% because of the monitor, 20% because of a disk drive, and 15% because of the microprocessor. If the problem is not in the monitor, what is the probability that it is in the hard drive? a) 0.150 b) 0.400 c) 0.417 d) 0.533 e) 0.650

15. If one card is randomly picked from a standard deck of 52 cards, the probability that the card be a red suit or a face (Jack, Queen, King) card is: a) 50% b) 61.5% c) 76.9% d) 88.5% e) 91.2%

16. Suppose you roll a six-sided die 10 times 16. Suppose you roll a six-sided die 10 times. What is the probability of getting three 5’s in those 10 rolls? a) 0.60 b) 0.30 c) 0.000618 d) 0.155 e) 0.930

17. One hundred people were interviewed and classified according to their attitude toward small cars and their personality type. The results are shown in the table below: Which of the following is true? a) Of the three attitude groups, the group with the negative attitude has the highest proportion of type A personality types. b) Of the three attitude groups, the group with the neutral attitude has the highest proportion of type B personality types. c) For each personality type, more than half of the 100 respondents have a neutral attitude toward small cars. d) The proportion that has a positive attitude toward small cars is higher among people with type B personality than among people with type A personality type. e) More than half of the 100 respondents have type A personality type and positive attitude towards small cars.