Probability with Random Variables

Jamie has 3 raffle tickets. One hundred tickets were sold. Her name was not drawn for the first prize. What is the probability that her name will be drawn for the second prize?

• 1/3

• 1/33

• 3/100

• 2/99

A company states that 2% of its computers are returned for defects. We take a sample of 100 computers to find the probability of 10 being defective. Is this a binomial distribution?

• No because there is not a fixed number of trials.

• No because there are more than 2 outcomes.

• Yes since there are a fixed number of independent trials, outcomes in 2 categories, and the probability of defect is constant.

• No since computers would not be independent.

If 1.5% of the bolts made by an automotive factory are defective, what is the probability that in a shipment of 200 bolts, there are 6 defective bolts?

• binompdf(200, 0.015, 6) = 0.050

• binomcdf(200, 0.015, 5) = 0.9176

• binomcdf(200, 0.015, 6) = 0.9676

• geometpdf(0.015, 6) = 0.0137

There is a multiple choice test with 4 choices per question. You must find probability of getting exactly 5 out of 12 questions correct. Which of the following is used to find the probability?

• binompdf

• binomcdf

• 1−binomcdf

• 1-binompdf

MC test with 4 choices per question find probability of getting at most 5 out of 10 questions correct. Which of the following would be used?

• binomcdf(10, 0.25, 4)

• binomcdf(10, 0.25, 5)

• 1−binomcdf(10, 0.25, 5)

• 1-binomcdf (10, 0.25, 4)

MC test with 4 choices per question, find the probability of getting exactly 7 out of 10 questions correct. Which of the following is the correct binomial?

• binompdf (10, 0.25, 7)

• binompdf (10, 0.70, 4)

• 1−binomcdf(10, 0.70, 7)

• 1-binompdf(10, 0.25, 7)

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 the tenth blood donor is the first donor with Type B blood?

• geometcdf(0.11, 10) = 0.7225

• 1 - geometcdf(0.11, 9) = 0.3119

• geometpdf(0.11, 10) = 0.0385

• .21

• .79

• .64

• .89

If we want to calculate the probability of rolling a 2 for the first time on the 6^th roll of a die, would we use the which distribution?

• geometric

• binomial

• normal