Compound events, the addition rule and mutual exclusivity
A synthetic classification records two properties for each ticket
Event A: the ticket is refundable. Event B: the ticket has a date
Let S be the sample space of all 24 recorded cases
The counts in the four disjoint regions are shown below
| Region | Count |
|---|---|
| A only | 4 |
| B only | 5 |
| A and B | 0 |
| Neither A nor B | 15 |
For the requested probability, select one recorded case uniformly at random