  In this Letter we validate experimentally the nonextensive statistical field
theory, a new general field-theoretic approach introduced recently in the
literature. With such an approach, we are capable of computing the critical
properties of nonextensive systems undergoing continuous phase transitions,
belonging to the new generalized O($N$)$_{q}$ universality class. We compare
the nonextensive critical indices values evaluated from the theory with those
already obtained in literature through experiments for various distinct
manganites presenting nonconventional critical behavior. The agreement is
satisfactory, whose relative errors are $< 5\%$ for the most of manganites
employed and as better as $|1 - q| < 1$ which is the limit of validity of the
theory. We present the physical interpretation of the experimental results and
of the theory through the general physical interpretation of the $q$-parameter.
