Question

Define the probability of an event E.

Answer 1

The probability of an event E is the ratio of number of trials in which event E happened to total number of trials.
P(E) = $\frac{\mathrm{Number}\mathrm{of}\mathrm{trials}\mathrm{in}\mathrm{which}\mathrm{event}\mathrm{happened}}{\mathrm{Total}\mathrm{number}\mathrm{of}\mathrm{trials}}$
Thus, $0\le P\left(E\right)\le 1$.