I just found the Statistics Index for the first time, and it's *great*! I wish I'd found it before... I took 3 college-level statistics courses, and yet I probably only know 10% of the terms in that window.
So, my suggestion is to break the terms up by their order of complexity, i.e. roughly by what level statistics course it would be introduced in. Then people who know very little about statistics could click "level 1" (or basic, beginner, etc.) off to the left and only the basic terms (sum, mean, standard deviation, etc.) would show up. You could then almost teach yourself statistics -- or at a minimum make a place in your head for concepts that you haven't learned yet -- by working through the different levels. "All" would be an option that would replicate the current list.
I also notice that "statistics", "probability", "residual", and "estimator" aren't in the list but should be. Don't need to put "number" in there, but starting at "statistics" would be a great place for newer users.