Is an open area of country with a low number of people, or low population density, living there. example: these areas make up 98% of the land in the u. s., but only 25% of the population live there.

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?