There are many methods by which scientists make observations. Three of these methods are controlled experiments, natural experiments, and models. Match each description of a procedure to the correct category of observation. Scientists develop a computer program that simulates the effects of changing temperature, pH, and other variables on coral. Public health researchers study the hospitalization rates for asthma before and after a city limits vehicle traffic. The world's most powerful supercomputers are updated moment to moment with new observations of weather conditions to generate a forecast. Scientists grow coral in labs and subject some to changes in water chemistry. natural experiment Press Space to open model Press Space to open controlled experiment Press Space to open