One of the Essential Differences Between Experimental Research and Correlational

Multiple Choice

One of the essential differences between experimental research and correlational research is that

A) in experimental research all variables are measured, whereas in correlational research at least one variable is manipulated
B) in experimental research, subjects are randomly assigned to the levels of the independent variable
C) experimental research uses random sampling, whereas correlational research uses random assignment
D) experimental research has higher external validity than correlational research