Is Probability Equally Distributed Among Unknown Options?

[KarimSafieddine]

Hey, I am new to this forum and I wanted to ask on something important for my work concerned with sociology.

I believe I know this but I am just making sure.

Let's say you don't know what a person is going to do next, but you do know it's between 3 options: A, B and C.
Do we say, in this case, that there's a 33% for each to occur?
Moreover, A and B always lead to one result Y.
Hence, Y has a 66% to occur?

That's it! I know it's very simple but I just have to get this off my head, I am not really sure this is the right section to place it though.

Thanks.

 

[Orodruin]

No, you cannot say this in general unless you have some additional information such as it being equally likely for the person to pick each of the alternatives. For example, in the cafeteria at my institute there are always three options for lunch, one meat dish, one fish dish, and one vegetarian. The probability that I pick the meat dish on any given day is of the order of 98%.

 

[KarimSafieddine]

No, you cannot say this in general unless you have some additional information such as it being equally likely for the person to pick each of the alternatives. For example, in the cafeteria at my institute there are always three options for lunch, one meat dish, one fish dish, and one vegetarian. The probability that I pick the meat dish on any given day is of the order of 98%.

What if you don't have any information to prove that one is more likely than the other? Does that render this unsolvable?

 

[Orodruin]

What if you don't have any information to prove that one is more likely than the other? Does that render this unsolvable?

Yes, in order to solve it you need to be supplied with the information that the alternatives are equally likely (or if not, what their probabilities are).