Question

The sum of probabilities of all outcomes in an experiment is__.

Answer 1

Probability of an event, P(E) = $\frac{\text{number of favourable outcomes}}{\text{total number of outcomes}}$

Let us take an example of tossing a coin. The possible outcomes of this experiment are {H, T}. That is, the total number of outcomes is 2.

Probability of getting a head, P(H) = $\frac{1}{2}$

Probability of getting a tail, P(T) = $\frac{1}{2}$

P(H) + P(T) = $\frac{1}{2}+\frac{1}{2}=1$

$\Rightarrow$ The sum of probabilities of all outcomes in an experiment is 1.