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Compound Events

vocab• Compound event- two or more events• Independent events- if the occurrence of one event

does not affect the probability of another• Dependent events- occurrence of an event affects

the probability of the occurrence of a second event.

Probability of an independent event• Find the probability of pulling two twizzlers if there

are 10 twizzlers in 40 pieces of candy and you put the candy back each time.

• P(twizzler first time) = 10/40 = ¼• P(twizzler 2nd time)( = 10/40 = ¼ (since we put the

first back, we still have 40 pieces of candy• P(twizzler twice) = P(twizzler) x P(twizzler)• P(twizzler twice) = ¼ x ¼ = 1/16

samples• You flip a coin 3 times. P(heads, heads, heads)

• You spin a spinner with red, blue, yellow, green and black parts. P(red then yellow)

• We are rearranging the seating chart. What is the probability of Grady being picked 2nd?

• What is the chance someone is picked first? 1/13

• So what is the chance someone is picked 2nd?• 1/12 because there is one less person

p. 599 quick check 2

Probability of an dependent event• We are picking seats. What is the probability that

Cecilia is picked first then Grady is picked second?

• What is the probability of Cecilia being picked? 1/13• What is the probability of Grady being picked? (1/12

because someone was already chosen)

• P (Cecilia, then Grady) = P(Cecila) x P(Grady after Cecilia is chosen)

• P(Cecilia then Grady) = 1/13 x 1/12 = 1/156

• There are 26 cards labeled A-Z in a bucket. What is the probability of finding T then E without replacing the first letter?

Questions?

homework

• P. 600-601 # 3-22 all