Probability Probability is the measure of how likely an event is. An event is one or more outcomes of an experiment. An outcome is the result of a single trial of an experiment.

What is the Probability of Drawing a club from a deck of cards? Events = 13 Outcomes = 52 Probability = 13/52 or ¼ or.25 or 25%

The Special Addition Rule If event A and event B are mutually exclusive, then More generally, if events A, B, C, … are mutually exclusive, then That is, for mutually exclusive events, the probability that at least one of the events occurs is equal to the sum of the individual probabilities.

In a group of 101 students 30 are freshmen and 41 are sophomores. Find the probability that a student picked from this group at random is either a freshman or sophomore. This makes sense since 71 of the 101 students are freshmen or sophomores Note that P(freshman) = 30/101 and P(sophomore) = 41/101. P(freshman or sophomore) = 30/ /101 71/101

The Special Multiplication Rule (for independent events) If events A, B, C,... are independent, then P(A & B & C &  ) = P(A)  P(B)  P(C)   What is the probability of all of these events occurring: 1.Flip a coin and get a head 2.Draw a card and get an ace 3.Throw a die and get a 1 P(A & B & C ) = P(A) · P(B) · P(C) = 1/2 X 1/13 X 1/6

Deviation Difference between the expected and the observed Difference between the expected and observed divided by the expected results time 100 to convert it to a percent Deviation = (50-45) / 50 Deviation = 10 % or coin tosses 45 heads 55 tails

As trials go up, deviation goes down 3 rd Rule of Probability for Biology Observed results get closer to expected results.

If a condom is 95 percent effective at preventing pregnancy, how many babies would you expect from 1 million condoms manufactured and used? 5 per 100 or 50,000 babies expected.