Conditional Probability “Given X, what is the probability of Y” Example: You’re picking one person at random from the class. Given the person in the class is a female, what the the probability he or she is blonde? What statisticians would write: P(Blonde | Female) – Tips: your total (n, or the number you divide by is only the girls! Not the whole class) – (# of blondes/#of girls)

From your pset! Given your cloth is from a hand loom, what is the probability that the quality is poor? Locate Handloom cloth How many total pieces are there made by a hand loom? How many of those are of poor quality?

Hints for solving Probability word problems When there is already a table, diagramming a tree is unnecessary Be careful to take the right total (n, denominator) – Especially in conditional probabilities! The simplest example of a conditional probability is the blonde | woman example we did above, store that in your head for easy reference, and so you’re not intimidated by the “ | “