The null hypothesis is that Nicholas is not a "psychic" and his predictions are no better than random guessing. It can be written mathematically as:
\[ \boxed{H_0: p = 0.5} \]
The alternative hypothesis is that Nicholas is a "psychic" and his predictions are better than random guessing. It can be written mathematically as:
\[ \boxed{H_1: p \neq 0.5} \]