1. Probability continues…

2. 0+37.4% A+35.7% B+8.5% O-6.6% A-6.3% AB+3.4% B-1.5% AB-0.6% 1.What is the probability a randomly selected donor is Type O-? 2.What is the probability a randomly selected donor is Type O, either + or -?

3. 1. Make a picture. 2. Make a picture. 3. Make a picture. We will be using Venn Diagrams.

4. 1. A probability is a number between 0 and 1. 0 ≤ P(A) ≤ 1 0 means the event can NEVER happen. 1 means the event will ALWAYS occur. 2. The set of all possible outcomes of a trial must have a probability of 1. P(S) = 1

5. 3. The probability that an event does not occur is 1 minus the probability that is does. P(A C ) = 1 – P(A) Example: The traffic light at the corner of College and Main is green 35% of the time. What’s the probability the light isn’t green when you get to College and Main?

6. 4. For two disjoint events A and B, the probability that one or the other occurs is the sum of the probabilities. P(A or B) = P(A) + P(B) Example: If P(green) =.35 and P(yellow) =.04, what is the probability the light is red?

7. 5. For two independent events A and B, the probability both A and B occur is the product of the probabilities of the two events. P(A and B) = P(A) x P(B) Example: What is the probability you find the light red both Monday and Tuesday?

8. What is the probability you don’t hit a red light until Wednesday? What’s the probability that you will have to stop at least once during the week?

9. Suppose 40% of the cars in your area are manufactured in the US, 30% in Japan, 10% in Germany, and 20% in other countries. If cars are selected at random, find the probability that:  You see two in a row from Japan.  The first US car is the third one you pick.  None of three cars came from Germany.  At least one of three cars is made in Germany.

10.  Note that the phrase at least is often a tip off to think about the complement.  Something that happens at least once does happen.  Happening at least once is the complement of not happening at all, and that’s easier to find.

11. In 2001, M&Ms decided to add a new color. When Japan was polled 38% chose pink, 36% chose teal, and 16% chose purple. 1. What is the probability a respondent selected at random chose pink or teal? 2. If we pick 2 respondents at random, what’s the probability they both selected purple? 3. If we pick 3 respondents at random, what’s the probability at least one picked purple?