Identify the following as an observational study or an experiment. A group of scientists looked at a group of older women (aged 74-92) in the U.S. who did not have dementia. Participants were followed from 2008-2018 and detailed cognitive function tests were done every year to determine whether they developed dementia. Participants' home addresses were noted, and mathematical models were used to estimate the air pollution levels at these locations over time. The scientists were interested in determining if air quality influenced the onset of dementia. Observational Study O Experiment