A study concludes that the use of pesticides is associated with the development of Parkinson's disease, a neurological disease that causes people to shake. The study reported that exposure to bug killers and weed killers is "associated with" an increase of 33% to 80% in the chances of getting Parkinson's. Does this study show that pesticides cause Parkinson's disease? Why or why not?

Select the correct answer below.

a. The study shows that pesticides cause Parkinson's disease. This was a controlled experiment because the only way to ensure exposure to pesticides is to use low levels of pesticides on the treatment group. Assuming all key features are satisfied, controlled experiments can conclude causation.
b. The study does not show that pesticides cause Parkinson's disease. The researchers did not administer a placebo along with the low levels of pesticides administered in the study. Therefore, a sufficiently robust control group was not established.
c. The study does not show that pesticides cause Parkinson's disease. This was an observational study because researchers could not have deliberately exposed people to pesticides. Observational studies cannot conclude causation.
d. The study shows that pesticides cause Parkinson's disease. Instatistics, the term "associated with" is synonymous with"causes." Therefore, it may be concluded that pesticides causeParkinson's disease.