mariomintchev
Stats Question
Real estate ads suggest that 63% of homes for sale have garages, 21% have pools, and 18% have both features. What is the probability that a home for sale has:
a) A pool or garage?
b) Neither a pool or garage?
c) A pool but no garage?
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mariomintchev
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For a I have to use the formula: P(A) + P(B) - P(A n B) =
Polrek
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|dw:1346193475482:dw|
mariomintchev
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Yeah, my teacher drew that out for us today. I don't really get what goes in the formula for part a though.
Polrek
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So the entire garage circle is 63% and the entire Pool circle is 21%. But these two percentages also contain the percentage of houses which have both. So you should add together the 63% and the 21%, and subtract the 18%, which is the intersection of A and B.
Polrek
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|dw:1346193785276:dw|
mariomintchev
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yeah i see that now.
Polrek
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|dw:1346193816687:dw|
mariomintchev
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for b, do i take 37 + 79 and then subtract 82?
mariomintchev
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or am i off?
Polrek
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I think you should just take the complement of your answer to A.
Polrek
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66% of houses have either a pool or a garage, so (1-0.66) = 0.44 will have none of these.
mariomintchev
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that's not it
mariomintchev
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i am given this formula though:
P(A)=1-P(A^c)
Polrek
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Yeah, so 1-P(A)' = P(A), and this works the other way. 1-P(A) = P(A)'
mariomintchev
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it's 0.34. you subtracted wrong.
Polrek
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Haha oh dear, more coffee required. Sorry. Do you get the idea though?
mariomintchev
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yeah, i'm getting it slowly but surely. this is my first time taking stats and i just started, so i'm getting used to it.
Polrek
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My advice is to get the hang of drawing those Venn Diagrams. They are really helpful.
mariomintchev
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can you help me with part c too?
mariomintchev
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hello?
Polrek
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This area, right? |dw:1346194888234:dw|
mariomintchev
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yeah
mariomintchev
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is it 0.21-0.18?
Polrek
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:)
mariomintchev
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sweet :)