1. Conditional Probability
Algebra II 12-2
Conditional Probability

2. Conditional Probability
The probability of an event occurring with something that limits the population
𝑃 𝐵 𝐴
The Probability of B given the event A
𝑃 𝐵 𝐴 = 𝑃(𝐴 𝑎𝑛𝑑 𝐵) 𝑃(𝐴)

3. 𝑃 𝑑𝑖𝑑 𝑐ℎ𝑜𝑟𝑒𝑠 𝑚𝑎𝑙𝑒 = 𝑃(𝑑𝑖𝑑 𝑐ℎ𝑜𝑟𝑒𝑠 𝑎𝑛𝑑 𝑚𝑎𝑙𝑒) 𝑃(𝑚𝑎𝑙𝑒)
Yes No
Male 7 8
Female 6
What is the probability of someone doing chores last night if they are male?
𝑃 𝑑𝑖𝑑 𝑐ℎ𝑜𝑟𝑒𝑠 𝑚𝑎𝑙𝑒
𝑃 𝑑𝑖𝑑 𝑐ℎ𝑜𝑟𝑒𝑠 𝑚𝑎𝑙𝑒 = 𝑃(𝑑𝑖𝑑 𝑐ℎ𝑜𝑟𝑒𝑠 𝑎𝑛𝑑 𝑚𝑎𝑙𝑒) 𝑃(𝑚𝑎𝑙𝑒)
7/28 15/28 = 7 15

4. Tree Diagram

5. In Portland when it snows only 2% of the time is it heavy.
When the snow is heavy schools are closed 95% of the time.
When snow is light they are closed 7% of the time.
What is the probability that the snow is light and school is closed?
6.86%

6. iRAT 𝑃 ℎ𝑎𝑠 𝑑𝑖𝑝𝑙𝑜𝑚𝑎 𝑃 ℎ𝑎𝑠 𝑑𝑖𝑝𝑙𝑜𝑚𝑎 𝑎𝑛𝑑 𝑒𝑥𝑝𝑒𝑟𝑖𝑒𝑛𝑐𝑒
𝑃 ℎ𝑎𝑠 𝑒𝑥𝑝𝑒𝑟𝑖𝑒𝑛𝑐𝑒 ℎ𝑎𝑠 𝑑𝑖𝑝𝑙𝑜𝑚𝑎
𝑃 ℎ𝑎𝑠 𝑛𝑜 𝑑𝑖𝑝𝑙𝑜𝑚𝑎 ℎ𝑎𝑠 𝑒𝑥𝑝𝑒𝑟𝑖𝑒𝑛𝑐𝑒
Top Experience, side diploma
Yes No 54 27 5 4

7. Problems
Page 656 #5-12