• One day at the dog park, John counted 127 dogs, of which 52 were off leash playing. Of the 52, 10 were Retrievers. He saw a total of 35 Retrievers.With this info, fill in the contingency table.

No leash Leashed Total

____________ _______ ___________ _________

Not a Retriever _______ ___________ _________

Total _______ ___________ _________

• Are the events not on a leash and retriever independent? _______

What is the probability that a dog is a Retriever is on a leash? _______

• What is the probability that a dog that is not on a leash is not a Retriever? P( ____ ) = _______

• What is the probability that a dog is on not a Retriever and on a leash? P(____) = ________

• A company has determined that 2 out of every 5255 bolts that it ordered is defective. What is the probability that that a worker will pick a bolt that is not defective? ________

• The probability that a worker will pick a bolt that is not defective is _________.

• Choose one for each of the following: Event A given that event B has already occurred, Event A or event B, The complement of A, Event A and Event B, Event B given that event A has already occurred.

• AB =
• AB =
• A' =
• A|B =
• B|A =

• Given that a box has 3 blue marbles, 2 red marbles, and 4 yellow marbles, use the probability formulas to answer the following questions.

Drawing a blue marble? P(____) = ____

Drawing a marble that is not red? P(____) = ____

Drawing a red and yellow marble? P(____) = ____

Drawing a red or blue marble? P(____) = ____

Drawing a red marble, put it back, and then drawing a yellow marble? P(____) = ____

Drawing a yellow marble, keeping it, and then drawing another yellow marble? P(____) = ____

Drawing a yellow marble, given that a red marble was drawn on the first draw and not replaced?

P(____) = ____

• What do we mean when we say the probability is conditional?_________________

• When we find conditional probabilities, do we need to check to see if they are mutually exclusive or if they are independent?
• How does this affect the calculation of probability. ______________