Approximately how many bankruptcy claims were filed in 2014?
a. 100,000
b. 250,000
c. 500,000
d. 1.1 million
e. 2.7 million

Chen's research team randomly assigned some newborns and their mothers either to a breastfeeding promotion group (where breastfeeding was encouraged, but not required) or to a normal pediatric care group (where breastfeeding was neither encouraged nor discouraged). which research method did they use?