Binomial and Geometric Random Variables

Which is the correct formula to find the probability that they will answer exactly 70 questions correctly?

• ₁₀₀C₇₀ (0.90)⁷⁰(0.10)³⁰

• ₁₀₀C₇₀ (0.10)⁷⁰(0.90)³⁰

• ₁₀₀C₁ (0.90)¹(0.18)⁹⁹

• ₉₉C₇₀ (0.10)³⁰(0.90)⁷⁰

If you want a certain number of successes in a set amount of trials, use the ???? method.

• Geometric

• Binomial

• Normal

• Poisson

If you want to know how many trials you will need before your first success, use the ???? model.

• Geometric

• Binomial

• Normal

• Poisson

The American Red Cross says that about 11% of the U.S. population has Type B blood. A blood drive is being held at your school. What is the probability that at least 2 of the first 10 blood donors has Type B blood? 

• 0.088

• 0.697

• 0.214

• 0.303 

When rolling a fair die 100 times, what is the probability of rolling a "4" exactly 25 times?

• 0.00983

• 0.167

• 0.25

• 0.0000756

Out of the whole population in the US, 13% are left-handed. In a sample of 30 randomly selected people, what is the probability that the 7 of them are left-handed?

• .0519

• .966

• .034

• 0.00229

Out of the whole population in the US, 13% are left-handed. If 30 people are randomly selected, how many left-handed people can you expect to get?

• We would expect to get 3.9 left-handed people

• We would expect to get 7.69 left-handed people

• We would expect to get 0.256 left-handed people

• We would expect to get 26.1 left-handed people

Is this a binomial experiment?

Shuffle a deck of 52 cards. Turn over the top card. Put the card back in the deck, shuffle again. Repeat the process 50 times. Let X = the number of aces you observe.

• Yes

• No, the trials are not independent.

• No, there are more than 2 outcomes

• No, the probability changes from trial to trial.

Suppose the probability of a student answering a multiple choice question correctly is 0.728. What is the expected number of questions it will take for the student to get a question correct?

• 0.78

• 0.95

• 1.21

• 1.37

• 1.58

What is the probability that event X will not be successful until the 3rd attempt?

• 0.002

• 0.054

• 0.318

• 0.522

• 0.868