Geometric vs Binomial AP Stats

At a certain intersection, the light for eastbound traffic is red for 15 seconds, yellow for 5 seconds, and green for 30 seconds.  Find the probability that out of the next eight eastbound cars that arrive randomly at the light,exactly three will be stopped by a red light.

• 0.254

• 0.147

• 0.027

• 0.1940

The owner of a pet store is trying to decide whether to discontinue selling specialty clothes for pets. She suspects that only 4% of the customers buy specialty clothes for their pets. What is the probability that she does NOT sell a garment until the 7th customer? Assume each customer is independent.

• 0.033

• 0.027

• 0.0313

• Not here

Which one of these variables is a binomial random variable?

• Time it takes a randomly selected student to complete a multiple choice exam

• Number of textbooks a randomly selected student bought this term 

• Number of women taller than 68 inches in a random sample of 5 women

• Number of CDs a randomly selected person owns

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

• Geometric

• Binomial

• Normal

• Calculator

• A

• B

• C

• D

• E

• A

• B

• C

• D

• F

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

• geometric

• binomial

counts the number of trials needed to obtain the 1st success. X = 1,2,3,…

• Geometric

• Binomial

• Both

• Neither

Each observation falls into one of two categories: “success” or “failure”

• Geometric

• Binomial

• Both

• Neither

The n observations are all independent.

• Geometric

• Binomial

• Both

• Neither