Mutually Exclusive Events

Mutually exclusive events exist when both events cannot occur simultaneously.

Examples

Example 1:

If a boy is born first, a girl cannot be born first. The occurrence of the first event precludes the occurrence of the second event.

We can add the probabilities of mutually exclusive events to find the probability of either one event or the second event occurring.

Example 2:

The probability of a boy
or a girl being the first
child is:

P(boy) + P(girl) = 1/2 + 1/2 = 1

Total equals certainty or Unity (100%).

Example 3:

Example of mutually exclusive
events with dominance gene
action. In soybean purple
flower color is dominant over
white.

P (purple genotype) = 3/4
P (white genotype) = 1/4

Purple is AA or Aa genotypes White is aa genotype:

P (purple) + P (white) = 3/4 + 1/4 = 1