Biology / Unit 5 Bio 1021 short lesson, about 20 seconds
The Rule of Addition
Captions available
The idea
The rule of addition, also called the sum rule, gives the probability of either of two mutually exclusive events by summing their probabilities.
In practice
A coin toss's chance of landing heads or tails is one half plus one half, or a certainty.
Where people slip
The rule of addition applies only to mutually exclusive outcomes — it is the wrong rule for combined, independent events.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for Biology