I toss two coins and look at the outcome.
I then tell you that at least one of the coins is showing up as "tails". What is the chance that the other one is showing "tails" as well?

(*from techInterview.org*)

(In reply to

re(4): Solution Using Real Prob/Stats by Charlie)

Charlie, you have a valid point here (and Lee, I think, has encapsulated it very well a couple of comments back).

(And I have read the full set of comments), but the issue that you are talking about is *definitely not* the issue that Eberhard and I were talking about. (Which translates to Lee's case (i) and maybe (ii)).

As evidence of what Eberhard was discussing, I will quote his earlier postings:

*...the real answer and why are as follows: The first know that each toss is concidered a seperate event by probability (known as independence)- meaning that the probability of either coin showing a particular side is always one half 1/2. Second know that when trying to determine if both will be the same side the probabilities are multiplied, i.e. 1/4 (this can be thought of as an ordered sequence).*

-- and --

*...what i think you might be missing is that HT and TH are functionally equivilant, meaning that there are 2 not 3 outcomes even in art's solution...*

*Edited on ***December 4, 2003, 7:44 am**