Which of the following research designs would allow systematic elimination of…

CONCEPT: A research design supports causal inference when it deliberately manipulates an independent variable and controls alternative influences on the outcome.

Control techniques such as random assignment, holding conditions constant, and comparison groups reduce the effect of extraneous variables.

APPLICATION: Among the listed designs, experimental research is organized around manipulation and control. Therefore, it permits systematic control of extraneous variables while the variables of interest are examined.

CONTRAST: The other designs have different defining purposes:

• Longitudinal research repeatedly observes units over time; its defining feature is temporal follow-up, not deliberate control of extraneous variables.

• Qualitative research investigates meanings, experiences, or processes through interpretive evidence; experimental control is not its defining structure.

• Correlational research measures how variables vary together without assigning treatments, so it does not by itself isolate causal effects from extraneous influences.

CROSS-CHECK: If a design can assign or manipulate the causal factor while keeping competing influences controlled, it satisfies the required criterion.

Result: Experimental research is the appropriate design.