Overall my experiment was successful and the hypothesis was shown as correct. In general, those who purchased more expensive menu items left food on their plates while customers ordering less expensive menu items ate all of their food. However, it is important to note that the more expensive menu items almost always offered more food for the customer than did cheaper items, thus making diners more likely to leave some food behind.
There were also noticeable trends within the most popular menu items, such as those ordering burritos ($8.50) general left more food behind than customers who ordered dinner combinations ($9.50). This may speak to the quality of Casa’s burritos, customer’s ability to become bored with their food, or to the amount of meat versus vegetables. Should this experiment to be reconstructed in the future; I definitely recommend a more sophisticated method of comparing consumption beyond item price. For example, I excluded from my findings customers who took food home, children who presumably have no interest in the cost or quantity of their meal, and two guests who received (and ate) meals that were contrary to their order.
One diner suggested taking into account the two baskets of chips his table consumed previous to their meals while another reminded me that he and his friends at less than normal because they had drank several beers beforehand. That group also suggested determining if all diners were sober (I assumed they were) as price and eating judgment can be affected while under the influence of drugs or alcohol.
I edited twenty plates into diptychs; here are four. Click for full size.