We have the test samples$\displaystyle X_{1},...,X_{n} $ from

$\displaystyle U(-\theta,\theta) $

with parameter $\displaystyle \theta $

Now show that $\displaystyle T = (3/n) (X^{2}_{1}+....+X^{2}_{n}) $

is an unbiased estimator for $\displaystyle \theta^2 $

My main problem is that I don't know which distribution this U stands for, is it the uniform distribution?

Can someone solve this plz