STAT 1350, Quiz #11, Summer 2014 Name _______________________________________

1. If I toss a fair coin five times and the outcomes are TTTTT, then the probability that tails appears on the next toss is
A) 0.5. B) less than 0.5. C) greater than 0.5. D) 0. E) 1.
Ans: A

2. If I toss a fair coin 5000 times
A) the number of heads will be close to 2500.
B) the proportion of heads will be close to 0.5.
C) the proportion of heads in these tosses is a parameter.
D) the proportion of heads will be close to 50.
Ans: B

3. When two six-sided die are rolled, the probability of getting a one on both is 1/36. This means that
A) of every 36 rolls, exactly 1 will have both die be one.
B) the odds against both die being one are 36 to 1.
C) in the long run, the average number of ones is 1/36.
D) in the long run the outcome that both die are one will occur on 1/36 of all rolls.
Ans: D

4. The odds against racehorse #9 (named “Southern Comfort”) winning this year’s Southeastern Derby are 7 to 3 (7:3 odds against winning). What is the probability that “Southern Comfort” will win this year’s Southeastern Derby?
A) 7/3 B) 3/7 C) 0.7 D) 0.3 E) 0.73
Ans: C

5. The Virginia State Lottery Commission states that the probability of winning a prize in their new scratch-off ticket lottery is 0.31. What are the odds against winning a prize in this new lottery game?
A) 69 B) 69 to 31 C) 31 to 69 D) 31 E) 1 – 0.31 = 0.69
Ans: B

6-10. Suppose you have a hat containing ten balls numbered from 0 to 9. You draw one ball at random and discover that it numbered 7.

6. If you place the ball back into the hat, what is the probability that you pull out the 7 ball on your next draw?
A) 0.5 (either you draw a 7 or you don’t) B) 1/10 C) 1/9 D) 0 E) 1
Ans: B


7. If you place the ball back into the hat, what is the probability that you pull out the 3 ball on your next draw?
A) 0.5 (either you draw a 3 or you don’t) B) 1/10 C) 1/9 D) 0 E) 1
Ans: B

8. If you do not place the ball back into the hat, what is the probability that you pull out the 7 ball on your next draw?
A) 0.5 (either you draw a 7 or you don’t) B) 1/10 C) 1/9 D) 0 E) 1
Ans: D

9. If you do not place the ball back into the hat, what is the probability that you pull out the 3 ball on your next draw?
A) 0.5 (either you draw a 3 or you don’t) B) 1/10 C) 1/9 D) 0 E) 1
Ans: C

10. If you do not place the ball back into the hat, what is the probability that you pull out even-numbered ball on your next draw?
A) 1/10 B) 1/9 C) 5/9 D) 5/10 E) 0
Ans: C

11. A collection of possible outcomes from a random phenomenon is called
A) a standard deviation.
B) a median.
C) an event.
D) an average.
E) a probability.
Ans: C

12. A _______________ for a random phenomenon describes all the possible outcomes and indicates how to assign probabilities to any collection of outcomes.
A) standard deviation
B) median
C) probability model
D) boxplot
E) scatterplot
Ans: C

13. A friend rolls a cheap 6-sided die many times. He reports that the probabilities of the possible outcomes are about as follows:

Outcome 1 2 3 4 5 6
Probability 0.2 0.2 0.2 0.1 0.1 0.2

Is this a legitimate assignment of probabilities?
A) Yes.
B) No, the faces must all have the same probability.
C) No, the 3 and 4 faces are opposite each other, so they must have the same probability.
D) No, the total probability for all faces is wrong.
E) No, not all the values given are possible values for a probability.
Ans: A