8 possibles: YYY, YYN, YNY, YNN, NYY, NYN, NNY, NNN.
Probability is binomial (only 2 possible answers). Chances of correctness:
All correct: 1/8; only 1 correct: 3/8; only 2 correct: 3/8; none correct: 1/8
At least 1 correct: 1-1/8=7/8;
At least 2 correct: 4/8=1/2;
At most 1 correct: 4/8=1/2;
At most 2 correct: 7/8.