Tutoring science, you might encounter experimental design. The tutor mentions the idea of a cross-sectional study.
Let’s imagine a characteristic of interest, C.
In its simplest form, a cross-sectional study will select two groups – group A with characteristic C, and group B without it. Then, the investigators will measure other characteristics of the groups, wondering if the presence or absence of the others is connected with the lack or presence of C.
Except for the absence or presence of C, the members of groups A and B will be similar.
Carlson, Neil R. Discovering Psychology. Needham Heights: Allyn and Bacon, 1988.Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.