S = sample space S = set of all possible outcomes S = {1,2,3,4,5,6}
E = event space E = set of items we want to happen (rolling a 5, or rolling an odd number) E = {1, 3, 5} note: the event of "rolling a 5" is a subset of "rolling an odd number" because 5 is odd
n(S) = number of items in the sample space n(S) = 6
n(E) = number of items in event space n(E) = 3
Divide the values to get the probability P(E) = n(E)/n(S) P(E) = 3/6 P(E) = 1/2 P(E) = 0.50 P(E) = 50%
The answer in fraction form is 1/2 The answer in decimal form is 0.50 The answer as a percentage is 50% These three values all represent the same idea, just written in different forms.
note: writing "P(E)" means "the probability of event E occurring", which I've defined as the event space above