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anonymous
 one year ago
HELP PLEASE!! Calculate probability of the independent event
P(A or B) when P(a)=.3 and P(B)=.7
anonymous
 one year ago
HELP PLEASE!! Calculate probability of the independent event P(A or B) when P(a)=.3 and P(B)=.7

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anonymous
 one year ago
Best ResponseYou've already chosen the best response.0You just have to multiply .3 by .7

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0oh ok well what about conditional probability with the same variables?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(A\cup B)=P(A)+P(B)P(A\cap B) $$ Since A and B are independent, \(P(A\cap B)=0\) So just SUM the independent probabilities.

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Yes. See  http://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Specifically, this section  http://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle#In_probability

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0ok what about if the variables are P(a)=.5 P(b)=.4 and then P(a and b)=.1?????

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I'm supposed to calculate the probability

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1You've got everything you need, P(a), P(b) and P(a and b)  see my formula above! Just plug in for P(a or b).

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(A\cup B)=P(A)+P(B)P(A\cap B)=0.5+0.40.1 $$ See how I did that?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0yes i just thought a and b were supposed to = P(A and B) but the answer is .8

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1What are you asking, not sure

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0the answer is .8 right?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0ok but theres nothing else i need to find? it just says calculate the probability

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Tell me the whole question to be sure

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Oh, those are different problems that P(A or B) Ok

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Do you know what P(AB) means?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0i know its a conditional probability problem

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(AB)=\cfrac{PA\cap B}{P(B)}=\cfrac{0.1}{0.4} $$ You can do the next. BRB

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0umm isn't that what i did?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0oh okay for 27 i got 4

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0if you can check the other ones i got .21 on 23 and on 25 i got 1 but if you can't then thank you for helping!

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Probabilities can not be greater than 1 so #27 is not 4

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1For #27 what do you have for P(BA)=P(B and A)/P(A) ?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0oh well you had .1/.4 so in 27 i just did .4/.1

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1No. The "" does NOT mean division. It means "given" P(AB) means Probability of event A given event B.

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(BA)=\cfrac{P(A\cap B)}{P(A)}\\ P(AB)=\cfrac{P(A\cap B)}{P(B)} $$ Do you see the difference above between the two?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Yes and that one is correct

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0i guess I'm not understanding this then

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1So we are dealing with probabilities of events. When we are given that an event occurs, we are asked what is the probability that the other will occur. If they are independent, then there is no effect. But if they are not independent, then conditional probability tells us that Probability of A given B is the Probability of A and B divided by the probability of B. Here is a visual dw:1433295585568:dw

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1That fraction is $$ P(AB)=\cfrac{P(A\cap B)}{P(B)} $$

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0that looks like alien writing to me

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(AB)=P(A \text{ given }B)=\cfrac{P(A\cap B)}{P(B)}=\cfrac{P(A\text{ and }B)}{P(B)} $$ Is this better?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0haha no I'm sorry... what does it look like with the values plugged in

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1$$ P(AB)=P(A \text{ given }B)=\cfrac{P(A\cap B)}{P(B)}=\cfrac{P(A\text{ and }B)}{P(B)}=.1/.4 $$ For #26

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1For #27 $$ P(BA)=P(B \text{ given }A)=\cfrac{P(A\cap B)}{P(A)}=\cfrac{P(A\text{ and }B)}{P(A)}=.1/.5 $$

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0it just made a lot more sense

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0so because (a and b) the value is .1 and P(a)=.5

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1#24 $$ P(AB)=P(A \text{ given }B)=\cfrac{P(A\cap B)}{P(B)}=\cfrac{P(A\text{ and }B)}{P(B)}=(0.3\times0.7)/0.7 $$ Notice that the result is independent of B because P(AB) = P(A)

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1This happened because A and B are Independent

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1If you understood that, then you can do #25 without any calculations

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Correct on your last comment

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0ok thank you i got it now
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