Answer:
The description correspond to an Observational Study.
Step-by-step explanation:
There two main types of experiments: observationals or experimentals. In the first ones, researchers do not imposed any kind of treatments in the populations they are examaning. On the contrary, in experimental studies, researchers apply different treatments (doses of a certain drug or levels a a toxin, for example) on a population and evaluate the response of each individual to the treatment.
Here, the research tries to determine if there is a relation between Parkinson´s disease and childhood head trauma so, the researcher only search to determine if individuals that already had Parkinson´s disease had a head traume when they were children. There no treatments imposed to the population of people with Parkinson´s disease so, this is an observational study.
