- Calculate probabilities of “equally likely” outcomes
Probability Values
A probability is always a number from [latex]0[/latex] to [latex]1[/latex], inclusive (which means that [latex]0[/latex] and [latex]1[/latex] are included). Probability may be written as a percentage, from [latex]0\%[/latex] to [latex]100\%[/latex], inclusive. We can also express a probability as a fraction or a decimal.
[latex]\text{Probability of }A = P(A) = \dfrac{\text{number of outcomes in event } A}{\text{number of all possible outcomes}}[/latex]
Sometimes we deal with situations that are more complicated than rolling a six-sided die or flipping a coin. However, the idea is the same—we think of the probability problem as two counting problems followed by the computation of a related fraction.
a numeric measure (the number of outcomes in the event divided by the number of possible outcomes in the sample space) of how likely the event is to happen