For our project, we asked as many seniors as we could to eat two brownies in a convenience sample that nevertheless managed to reach a significant fraction of the senior class. The experiment participants were able to volunteer to eat the brownies. Siobhan and I baked a batch of copycat Cosmic Brownies, and bought a box of manufactured brand name Cosmic Brownies. We assigned every volunteer to a random number, and this number determined in which order they would eat two brownies. There were 4 numbers, 1-4, with:
1 = Cosmic Brownie first, then one of our copycats.
2 = Our copycat first, then one Cosmic Brownie.
3 = Two Cosmic Brownies.
4 = Two copycat brownies.
After the subject had eaten both of the brownies, we asked them "which brownie, the first or second, that [they] prefer", as well as "which brownie [they] believe to be the store bought brownie," regardless of whether they had actually eaten a store bought brownie or not.
Due to the not-so-subtle difference in the bittersweet frosting on top of our scratch brownies, the difference between the two was recognizable, and this is reflected in the data.