I think the way you put it makes sense, and if you put the number in, you get to the right conclusion. The way I think about this is slightly different, but (I think) equivalent:
Let {Hn} be the set of all possible Persons, and {pn} the probability of them existing. The probability, that you are the person Hmis pm∑npn. Lets say some but not all possible people have red hair. She subset of possible people with red hair is {Hs}⊆{Hn}. Then the probability, that you have red hair is:∑sps∑npn.
In my calculations in the post, the set of all possible people is the one solipsistic guy, and Np people in the non-solipsistic universe. (with their probability of existence being cs and (1−cs) ). So the probability, that you are in a world, where solipsism is true, is cscs1+(1−cs)Np.
I think the way you put it makes sense, and if you put the number in, you get to the right conclusion. The way I think about this is slightly different, but (I think) equivalent:
Let {Hn} be the set of all possible Persons, and {pn} the probability of them existing. The probability, that you are the person Hm is pm∑npn. Lets say some but not all possible people have red hair. She subset of possible people with red hair is {Hs}⊆{Hn}. Then the probability, that you have red hair is:∑sps∑npn.
In my calculations in the post, the set of all possible people is the one solipsistic guy, and Np people in the non-solipsistic universe. (with their probability of existence being cs and (1−cs) ). So the probability, that you are in a world, where solipsism is true, is cscs1+(1−cs)Np.