Introduction to Probability

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1. A fair coin is tossed 150 times. The results are 70 heads and 80 tails. What is the probability that the next toss is heads?

P(A) = 0.467
P(A) = 0.500
P(A) = 0.700
P(A) = 0.533


2.Which of the following answers cannot represent the probability of an event occurring?
P(A) = 0.524
P(A) = 1.000
P(A) = -0.147
P(A) = 0.000


3. A couple decides that they want to have 3 children. What is the probability that they have at least 3 girls?

P(A) = 0.625
P(A) = 0.125
P(A) = 0.500
P(A) = 0.725


4. Construct the sample space for rolling a pair of dice. What is the probability of rolling 7?

P(A) = 0.167
P(A) = 0.833
P(A) = 0.333
P(A) = 0.500


5. As part of an in class experiment, students observed the number of people who ran the stop sign on the Ring Road. They used this experiment to estimate the probability a person driving on campus will run that stop sign. What type of probability did they use?

Classical Probability
Relative Frequency
Subjective
No probability was used at all


6.The sample space for rolling a single die is {1, 2, 3, 4, 5, 6}. Which of the sets below represents the complement to the event A = {1, 4, 6}?

{1, 2, 3}
{3, 5, 6}
{2, 4, 6}
{2, 3, 5}


7.This question has 4 responses. Assuming you guess at the answer what is the probability that you get the question correct?

P(A) = 0.500.
P(A) = 1.000.
P(A) = 0.200.
P(A) = 0.250.


8.When teaching Statistics one semester, an instructor's grade distribution was as follows: 7 A's, 10 B's, 8 C's, 2 D's and 3 F's. If a student is selected at random, what is the probability that the student received an B?

P(A) = 0.500
P(A) = 0.767
P(A) = 0.333
P(A) = 0.358



9. In her August 10, 1997 column for Parade magazine, Marilyn vos Savant was posed the question "Your dog has a litter of four, is it most likely that two are males and two are females?". Using probability theory, is the answer yes or no? Assume male and female births are equally likely, (she did) and draw out the sample space. Hint: Consider the complement, not having two females and two males.  Alternate hint:  Is the probability of 2 females & 2 males greater than 50%?

Yes
No