This seems OK up to here, you want to generate samples from a beta distribution (I would use whatever function is provided by the software you are using for this. That would be betarnd(..) for matlab and octave)

[Now you have lost me-- i want to group items together whose distribution of scores is also beta, but only with a lot of the mass centered around the mean and tailing off on both ends (like a hump). these groupings of beta distributions should (i'm pretty sure) naturally form in my data, so my question is: is there a method to sample from my population that gives me a smaller population with a given distribution? any starting point would help...thanks!

CB