Chapter 4.3 and Conditional Probability · 2020. 12. 23. · ex: A coin is flipped and die is...
Transcript of Chapter 4.3 and Conditional Probability · 2020. 12. 23. · ex: A coin is flipped and die is...
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Chapter 4.3Multiplication Rules
and Conditional Probability
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Define the following in your notes: independent events, dependent events, conditional probability
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Multiplication Rulesfinds prob. of 2+ events occuring in sequence
ex: Tossing a coin AND rolling die at same time
Mult. Rule #1When 2 events are independent, the prob. of both occuring is:
P(A and B) = P(A) P(B)
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ex: A coin is flipped and die is rolled. Find prob. of tails on coin and a 4 on die.
ex: A card is drawn from deck, replaced, then a 2nd card drawn. Find the prob. of getting a queen then a black card.
ex: A jar with M&M's has 3 red, 2 blue and 5 brown. One is selected, recorded, then replaced. Then a 2nd is selected. Find the prob:
a.) 2 blue's.
b.) 1 blue then 1 brown.
c.) 1 red then 1 blue.
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ex: A poll found 46% of Americans are greatly stressed once a week. If 3 people selected randomly, find prob. that all 3 are greatly stressed once a week.
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Dependent Eventsex: Drawing a card, not replacing, then drawing anotheruse same mult. rule (but make sure 2nd prob. is modified)
ex: If a card is drawn from a deck, not replaced, and then a 2nd card drawn, find prob. that an ace is drawn 1st, then a king.
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ex: State Farm found that 53% of residents had home insurance and of these, 27% also had auto. If a resident is selected at random, find prob. that he/she will have both home and auto insurance with State Farm.
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ex: 3 cards are drawn from deck and not replaced. Find prob. of getting:
a.) 3 jacks.
b.) an ace, king and queen in order.
c.) a club, spade and heart in order.
d.) getting 3 clubs.
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ex: Box 1 has 2 red and 1 blue chips. Box 2 has 3 blue and 1 red chips. Toss a coin. If heads, select a chip from box 1. If tails, select a chip from box 2. Find prob. of selecting a red chip.
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ASSIGNMENTp. 228 #16, 10
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P(A and B)P(A)
ex: A box has black and white chips. A person selects 2 w/o replacement. If prob. of selecting B & W is and prob. of select a B on 1st draw is , find prob. ofselecting W on 2nd draw if 1st chip was B.
1556
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Conditional Probability P(B|A) "probability of B given A"event B occurs after event A
P(B|A) = _________
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ex: In Ytown, the prob. of parking in a no parking zone and getting a ticket is 0.06, while prob. parking in no parking zone is 0.20. If you park in a no parking zone, find prob. of getting a ticket.
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ex: A survey asked 100 people if women in Army should be in combat.
Gender Yes No TotalMale 32 18 50Female 8 42 50
Total 40 60 100
Find the prob.:a.) Person answered yes, given the person was female.
b.) Person was male, given that the person answered no.
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"At Least" Examples
ex: Draw 4 cards from a deck with replacement. Find prob. of drawing at least 1 ace.
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ex: Coin is tossed 5 times. Find prob. of getting at least 1 tail.
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ex: Suppose 3% of ties sold in America are bow ties. If 4 random customers purchase ties, find prob. at least 1 bought a bow tie.
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ASSIGNMENTp. 229 #11, 12, 1820, 23, 2527,
32 (a&b), 34, 35