Answer:
Prospective study
Step-by-step explanation:
Prospective
A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s) (A group of researchers wants to determine whether certain dietary factors are associated with the risk of attention deficit hyperactivity disorder (ADHD)) . The study usually involves taking a cohort of subjects(500 healthy newborn babies) and watching them over a long period(10 years). The outcome of interest should be common; otherwise, the number of outcomes observed will be too small to be statistically meaningful (indistinguishable from those that may have arisen by chance). Prospective studies usually have fewer potential sources of bias and confounding than retrospective studies.