let $T$ be the splitting field over $\mathbb Q$ of a polynomial $f(x)=x^n+\sum_{i=0}^{n-1} a_i x^i \in \mathbb Q[x]$, where $a_i$ are integral for the prime numbers 2 and 3 and let $f \text{ mod }3$ be irreducible.
Now it is said, that 3 is unramified in $T$.