Probability

The expected mean is 8% x 15 or 1.2 accidents.
The standard deviation expected is sqrt( p (1-p) N ) = sqrt ( .08 * .92 * 15 ) = 1.05.
The z-score for this would be (3-1.2)/1.05 = 1.95
That z-score corresponds with a probability of 2.56%