The p.d.f. of a continuous random variable \( X \) is given by
\[
f(x) =
\begin{cases}
\frac{1}{2} & \text{if } 0<x<2, \\
0 & \text{otherwise},
\end{cases}
\]
and if
\[
a = P(X \leq \frac{1}{2}), \quad b = P(X>\frac{1}{2}),
\]
then the relation between \( a \) and \( b \) is