A study of the relationship between two variables that the investigator does not control is known as a

A) random assignment.
B) correlational study.
C) double-blind experiment.
D) case history.

The study described in the question, where the investigator only observes the relationship between two variables and does not control them, is a correlational study. A) random assignment refers to assigning participants to different groups in an experiment randomly, B) double-blind experiment is an experimental design where both the participants and the experimenters are unaware of the group assignments, and D) case history is a detailed analysis of an individual or group usually used in clinical settings.