Help with probability?

- anonymous

Help with probability?

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- schrodinger

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- anonymous

@uri @perl @ganeshie8

- anonymous

I will help :) What's the problem

- anonymous

Choose a row and column and compare P(A | B) with P(B | A). Explain what each probability means in the context of the situation and data you collected.:

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- undeadknight26

Alright do you know how to find the probability of this? Or is that what you need help with?

- anonymous

I'm just kinda lost on what column to choose.

- anonymous

And where to go from there.

- undeadknight26

Choose any one

- anonymous

Okay, how about Nikon professional photographers to Canon professional photographers?

- anonymous

@undeadknight26

- undeadknight26

One second please :)

- anonymous

Okay, sorry!

- undeadknight26

It's fine m8 :)

- undeadknight26

I'm just refreshing my memory on probability lol

- undeadknight26

Well you chose the Professional column right?

- anonymous

Yes!

- undeadknight26

This question is busting my brain ._.
@acxbox22 @surjithayer @sleepyjess @dan815 @geny55 @gabylovesu @campbell_st @Nurali @robtobey

- undeadknight26

Sorry mate I thought I could do it but I forgot everything about probability :/

- perl

Would you like help with this?

- anonymous

Yes please!

- perl

you want to compare P(A|B) and P(B|A)
First lets define A and B

- anonymous

Okay, how?

- perl

Let
A = professional
B = Nikon brand
Once you define A and B, then it forces the complements to be:
A' = non professional
B' = the other brand Canon

- anonymous

Okay got it. So how would I label that with P(A | B) and P(B | A)?

- perl

P(A|B) means the probability of event A given that you know event B has already occured. On the table this means we only look at event B's row or column

- anonymous

Okay, so P(8|12)?

- perl

P( A|B) = P( professional | Nikon brand )

- anonymous

Oh so I don't need to put any numbers in?

- perl

The given part means that we only look in the row 'Nikon'

- anonymous

Oh okay! So P(Profesional | Nikon) and P(Nikon | Profesional)?

- anonymous

Professional*

- perl

P( A|B) = P( professional | Nikon brand )
we look only in the Nikon row. http://prntscr.com/7kwtse
therefore P(A|B) = 8/10

- perl

the `|` symbol means 'given' .

- anonymous

OHH I understand!

- anonymous

And then vise versa for P(B | A)?

- perl

yes

- anonymous

Okay, what about P(A∩B) with P(A∪B)?

- perl

P( B|A) = P( Nikon brand | Professional )
http://prntscr.com/7kwury
8/12

- anonymous

Got it! What about my question above?

- perl

Okay, what about P(A∩B) = 8/20
P(A∪B) = (8 + 2 + 4) / 20

- anonymous

That's it?

- perl

little more detail here

- perl

P(A∩B) : probability of professional `and` Nikon
http://prntscr.com/7kwx9w
= 8/20
P(A∪B) : probiablity of professional `or` Nikon
http://prntscr.com/7kwxo7
= (8 + 2 + 4) / 20

- perl

You can think think of it in terms of intersection of row and column
P(A∩B) http://prntscr.com/7kx0gv

- anonymous

Ohh okay! So I said...
Compare P(A∩B) with P(A∪B), and explain what each probability means in the context of the situation and data you collected.:
P(A∩B) = 8/20 (probability of professional and Nikon). Here, were only looking at the eight professional Nikon photographers. P(A∪B) = (8 + 2 + 4) / 20 (probability of professional or Nikon). Here, we’re using data from the professional column of Canon and Nikon plus Nikon’s two non-professionals.

- perl

Looks good :)

- anonymous

Okay great! Thank you so much! Only three more homework assignments till I graduate!

- perl

A∩B is also called `A intersect B` or `A & B `
A∪B is called `A union B` or `A or B `

- perl

Good luck :)

- anonymous

Alright, it's in my notes now. Thank you!

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