Question

The sum of probabilities of all elementary events of an experiment is ______.

Options

• 1

• 0

• `1/2`

• –1

Answer 1

The sum of probabilities of all elementary events of an experiment is 1.

Explanation:

Elementary events are the individual outcomes that make up the sample space; their probabilities are non‑negative and together account for the sure event (the sample space), whose probability is 1.

For example, for a fair coin P(H) + P(T)

= `1/2 + 1/2`

= 1