Consider the uniform distribution on $\displaystyle [0,\theta]$

Define $\displaystyle G_n=\sqrt[n]{Y_1\cdots Y_n}$ (i.e. the geometric mean) and the Ys are independent rvs.

Is $\displaystyle G_n$ a sufficient estimator?

I just really have a hard time with the concept of sufficiency. I basically just try to use the factorization theorem without understanding what I'm doing, and I am struggling to do so with the geometric mean. I was thinking to use an indicator function for y from 0 to theta?

EDIT: Maybe I am having trouble because it is not sufficient. It seems like averages are not going to tell all the information relevant to find upper bounds.