III. Simple Discussion
Probability Rules
Probability is a number. It is always greater than or equal to zero, and less than or equal to one. This can be written as \( 0 \leq P(A) \geq 1 \). An impossible event, or an event that never occurs, has a probability of 0 . An event that always occurs has a probability of 1 . An event with a probability of 0.5 will occur half of the time.
Probability of Simple Events
Any event consisting of a single point of the sample space is known as a simple event in probability.
Examples:
1. The probability of getting a \( \mathbf{5} \) in rolling a die is a simple event.
2. The probability of getting a TAIL in tossing a coin is a simple event.
If each of the outcomes in a sample space is equally likely to occur, then the probability of an event is given by
\[
P(E)=\frac{\text { number of ways the event can occur }}{\text { total number of possible outcomes }}
\]
