What is the probability of picking an s in the word Mississippi?

The probability of picking an 's' in the Word Mississippi is 100% - you will always find one ... eventually.

However if you mean with single choice from the 11 characters of the Word Mississippi, then the probability is 4 chances in 11 which is just over 36% or a probability of 0.363636 recurring.

My odd answer illustrates the need to pose questions without ambiguity.

Beano GB