• Provide examples of finding probabilities of compound events using tree diagrams
This packet introduces you to tree diagrams as a way of finding probabilities of compound events. There is a powerpoint slideshow of definitions, and a video of some examples.
This packet introduces you to tree diagrams. Some terms that may be new are:
Source: Greene
This video has the definition of a tree diagram.
Source: Greene
This video shows you an example of disease test results and actual disease status.
Source: Greene
Consider the following situation:
First, you flip an unfair coin, getting either a heads or a tails, with unequal probability (p = .7 for heads, p = .3 for tails). Next, you pull a marble out of a bag. There are three colors: blue (p = .4), red (p = .5), and yellow (p = .1). Draw a tree diagram of this situation, and then figure out the probability of getting a head and a blue. Also, figure out the probability that you get a tails and a yellow.
Source: Greene
Consider the following situation:
First, you flip an unfair coin, getting either a heads or a tails, with unequal probability (p = .7 for heads, p = .3 for tails). Next, you pull a marble out of a bag. There are three colors: blue (p = .4), red (p = .5), and yellow (p = .1). Draw a tree diagram of this situation, and then figure out the probability of getting a head and a blue. Also, figure out the probability that you get a tails and a yellow.
Tree Diagram:
___p = .4_____BLUE
___p = .7______H___p = .5____RED
 ___p = .1_____YELLOW

 ____p = .4_____BLUE
_____p = .3_______T____p = .5____RED
____p = .1_____YELLOW
P(H and BLUE) = We look for the heads outcome for the first event, which has p = .7. Then we see the blue probability coming off of the heads outcome is .4. Therefore, we multiply these two together. .7*.4 = .28.
P(T and YELLOW) = We look for the tails outcome for the first event, which has p = .3. Then we see the yellow probability coming off the tails outcome is .1. Therefore, we multiply these two together. .3*.1 = .03.
Source: Greene