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COMM 290 - Probability

# COMM 290 - Probability - P1 head on 2 tosses = P HT or TH =...

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COMM 290 – Probability October 29 th , 2010 Coin Toss Example 1. Toss a fair coin once = ( ) PH 12 intuition 2. Toss a fair coin twice ( ) P 1 H on two tosses Sample Space HH, HT, TH, TT Alternate Solution H H T H T T = + = ∴P1 head on 2 tosses 14 14 24 3. Toss an unfair coin twice = = P1 head on 2 tosses if PH 13 and PT 23?

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Solution By Tree H H T H T T = + = ∴P1 head on 2 tosses 29 29 49 Probability Summary 1. Multiply across branches 2. Add going down the end of branches Sample Space A list of all possible ways an experiment can occur Event A subset of the sample space Probability 0 1 0% 100% Impossible Certainty
Probability Approaches Intuition, tree, formula Example: toss a fair coin twice.

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Unformatted text preview: P1 head on 2 tosses = ( ) P HT or TH = + PHT PTH = + = 14 14 24 Rule = + PA or B PA PB Example: toss a fair coin once; pick one ball from a bag containing 8 white and 2 red balls. P(H or W)? Possible solution: = + PH or W PH PW = + 12 810 = . ( ) 1 3 not possible Correct Solution: W H R W T R = -= ∴PH or W 1 220 1820 = +-PH PW PH and W = +-12 810 820 = 1820 Summary 1. P(A or B) = + ( ) PA P B if A, B are mutually exclusive 2. P(A or B)= P(A) + P(B) – P(A and B) Venn: 3. Independent: P(A and B) = × PA PB 4. Dependent: P(A and B) = ( )× ( ) P A P B|A...
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COMM 290 - Probability - P1 head on 2 tosses = P HT or TH =...

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