Question

Help me find Q please!!
For mutually exclusive events R1, R2, and R3, we have P(R1)=0.05, P(R2)=0.4, P(R3)=0.55. Also P(Q|R1)=0.5, P(Q|R2)=0.7, and P(Q|R3)=0.4.

Find P(R2|Q).

Answer 1

what did you do? where is the other post hehe

Answer 2

I reposted, i really need to find it haha but i know what to do once i get Q

Answer 3

So you didn't find what i told you hehe

Answer 4

Im trying to! haha I've been searching everywhere

Answer 5

Okay! well unfortunately i forgot lot of stuff hehe

Answer 6

ahh found it i think @xapproachesinfinity

Answer 7

Okay write down here and see how can we do it

Answer 8

Its P(R2|Q)= P(Q|R2)/(P(Q|R1)*R1+P(Q|R2)*R2+P(Q|R3)*R3)

Answer 9

Are you sure lol that doesn't look good to me

Answer 10

what's the original thing you found

Answer 11

let the question open hehe

Answer 12

haha whoops i closed it but i found it on my notes for my online class! i was hoping it's right

Answer 13

you are taking this course online? not quite good

Answer 14

P(R2/Q)=P(Q/R2)P(R2)/ (P(Q/R2)P(R2)+P(Q/ not R2)P( not R2)
i guess this the formula

Answer 15

1-P(R2)=P( not R2)=1-0.4=0.6

Answer 16

what do you mean not R2?

Answer 17

Complement of R2 is not R2
it mean R2 not accuring

Answer 18

they usually denote with a c on top if you check your text book you will find it that way

Answer 19

let's event A is it is raining today
not A will be it is not raining do you get it?

Answer 20

i think this is now simple!

Answer 21

we already got P(Q/R2)=0.7

Answer 22

we know P(R2)=0.4

Answer 23

we are missing one thing
P(Q/not R2)

Answer 24

P(Q/not R2)=P(Q and not R2)/P(R2)
P(Q and not R2)=P(Q)P(not R2)

Answer 25

but we still dont know P(Q)?

Answer 26

Darn it! again P(Q) is missing
now that i think about it there is a reason why they give you all those probab
so you can use it to get that P(Q)

Answer 27

I would like to play with this little more but im running out of time here

Answer 28

@jdoe0001

Answer 29

Note that P(Q/R3)=P(R2)

Answer 30

So P(Q/R3)=P(Q)P(R3)/P(R3)=P(R2)
hence P(Q)=P(R2)=0.4

Answer 31

is what you wrote correct! make sure

Answer 32

Ill double check I have to go run an errand but thank you so much!

Answer 33

we almost done! just plug the numbers!
and you are welcome