  For a polynomial $F(t,A_1,\ldots,A_n)\in\mathbf{F}_p[t,A_1,\ldots,A_n]$ ($p$
being a prime number) we study the factorization statistics of its
specializations $$F(t,a_1,\ldots,a_n)\in\mathbf{F}_p[t]$$ with
$(a_1,\ldots,a_n)\in S$, where $S\subset\mathbf{F}_p^n$ is a subset, in the
limit $p\to\infty$ and $\mathrm{deg} F$ fixed. We show that for a sufficiently
large and regular subset $S\subset\mathbf{F}_p^n$, e.g. a product of $n$
intervals of length $H_1,\ldots,H_n$ with
$\prod_{i=1}^nH_n>p^{n-1/2+\epsilon}$, the factorization statistics is the same
as for unrestricted specializations (i.e. $S=\mathbf{F}_p^n$) up to a small
error. This is a generalization of the well-known P\'olya-Vinogradov estimate
of the number of quadratic residues modulo $p$ in an interval.
