Researchers at East Tennessee State University wanted to test their prediction that offering incentives would encourage donations. Members of the "treatment group" were offered a lottery ticket if they donated. Members of the "control group" were offered no special incentive. The researchers found that offering a lottery ticket increased donations. What method of quantitative research did they use?

The Inca are known for domesticating animals for transportation and for praying to the sun god Inti. The Inca had an elaborate road transportation network used for trading and communication. The Inca domesticated the alpaca and the llama as beasts of burden.

The Mayan people cultivated maize on a large scale as this was one of their favourite foods. In order to feed a rapidly growing population, there needed to be many agricultural workers.