2 In a study on the effect of maternal exposure to cigarette

#2 In a study on the effect of maternal exposure to cigarettes on the risk of preterm birth, the number of preterm births occurring among 130 women who smoked during pregnancy between 2010 and 2012 was compared to the number of preterm births among 192 women who did not smoke during pregnancy during the same time period. In a second study, the pregnancy medical records of 55 women who gave birth to premature infants were compared to those of 98 women who did not have a premature infant in order to assess if the women smoked during pregnancy. Which of the following statements is correct? The first study was a controlled experiment, while the second was an observational study. The first study was an observational study, while the second was controlled experiment. Both studies were controlled experiments. Both studies were observational studies.

Solution

The first study was an observational study and the second study was controlled experiment.