Final answer:
The experimental design described where the size of tableware is manipulated and the amount of food consumed is measured in a controlled setting is an example of a controlled experiment.
Step-by-step explanation:
The description provided is an example of controlled experiment. A controlled experiment is one in which participants are divided into an experimental group and a control group. The key feature of this type of experiment is that it manipulates an independent variable and measures the effect of this manipulation on a dependent variable, while holding all other variables constant. In the scenario described, the use of differently sized tableware as the independent variable and the amount of food consumed as the dependent variable are being tested. Since there's a manipulation of the environment, and other variables are controlled, this qualifies as a controlled experiment, making it different from natural or field experiments, observational studies, and other methods that do not involve this level of manipulation.