69. The National Children’s Study (NCS), the largest and most detailed study ever on children’s health in the United States, is examining environmental effects on a large sample of children (from roughly 100,000 families) from before birth to age 21 years. Learn more at www.nationalchildrensstudy.gov.
69.
(a) This is an observational study because there was no manipulation of environment or assignment of treatment.
(b) This is a prospective study.
(c) This study could not have been done as an experiment because one cannot manipulate or control the environment throughout the 21+ years.