Jeff is a researcher who wants to understand the effect of child abuse on an individual's personality and attitude. He forms two groups of participants for his study. The first group includes people who were abused during their childhood and the second group includes people who had normal childhoods. This type of division of people based on actual differences rather than through random assignment is referred to as which type of design

Ex post facto

Explanation:

Ex post facto may be considered a form of research pattern whereby the facts are already established beforehand. That is findings about a particular phenomenon or occurence begins only after the facts about the incident or phenomenon has been established. It is also called after the fact research whereby the researcher only delves into finding patterned after the facts have been established without the knowledge, understanding of the researcher. Ex post facto is used to understand the pattern or effect rather than if the fact or problems truly exists.

explanation:

with the profits from the european sales, merchants purchased europe's manufactured  goods, including tools and weapons. then the merchants shipped those manufactured  goods, along with the  american  sugar and rum, to west africa where they were bartered for  slaves.