Tree Diagram

[nasi112]

If we have the tree diagram above and we want to find [MATH]P(Medium)[/MATH]
Is it correct to say?

[MATH]P(Medium) = 0.25 + 0.125 = 0.375[/MATH]

 

[Steven G]

No.

Suppose it was a 1 in a million chance that someone chose pepsi. Would the .25 have the same weight as it would if choosing pepsi was 6 in 10?

 

[Steven G]

I have a better question. What is the probability that someone chooses a small, medium or large drink. Would it be .6+.25+.15+.85+.125+.025?

 

[pka]

View attachment 26350If we have the tree diagram above and we want to find [MATH]P(Medium)[/MATH]

What is $\mathscr{P}(M)=\mathscr{P}(M\cap P)+\mathscr{P}(M\cap C)=~?$

 

[nasi112]

I have a better question. What is the probability that someone chooses a small, medium or large drink. Would it be .6+.25+.15+.85+.125+.025?

Thanks Jomo for showing up. In this case, the probability will be 2 which makes no sense.

What is $\mathscr{P}(M)=\mathscr{P}(M\cap P)+\mathscr{P}(M\cap C)=~?$

Thanks pka for showing up. This means

[MATH]P(medium) = (0.6)(0.25) + (0.4)(0.125) = 0.2[/MATH]
If this is the correct answer, then in which cases I should sum the probabilities in the 2nd group.

By groups, I mean Pepsi and Cola are first group, and S, M, L are second group.

 

[lex]

I always put in the outcomes and their probabilities, so that I'm now ready to face any question.

E.g. your question P(Medium). Just go through the outcomes and add the ones which contain M(edium):
0.15 + 0.05

You could I suppose answer a conditional probability question: e.g. given that it is a Pepsi, what is the probability it is Small or Medium,
by just adding 0.6 and 0.25.
But conditional probabilities can be done using my two columns too, so it's not necessary to do it that way.

 

[nasi112]

Thanks a lot lex. I grasped it.