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Conditional Probability. “Given X, what is the probability of Y” Example: You’re picking one person at random from the class. G iven the person in the class is a female, what the the probability he or she is blonde? What statisticians would write: P(Blonde | Female)
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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 “ | “
