A Young Boy Is Fishing Off the End of a Dock

Essay

A young boy is fishing off the end of a dock. He estimates that for one out of every 15 times he casts his line, he gets at least a nibble from a curious fish. He is going to cast his line 50 times before he switches to toad hunting.
-If he gets only 5 nibbles on his line, is that a signal that he is having less success than usual?
Justify your answer.