A student is concerned with the amount of air pollution students are exposed to in the school's parking lot after school. The student conducts an investigation to compare the quantity of particulate matter released from the diesel-powered buses, natural gas powered buses, and the large and small cars as they idle waiting to pick up students. To make measurements, a small
piece of white fabric is used to collect particulate matter from the tailpipe of each vehicle as it idles for five minutes. Each piece of fabric is then analyzed to measure the amount of particulate
matter it collected
(9) Identify the dependent variable, the hypothesis, a possible control group in the investigation