In which of the following research methods, manipulation and control of…
2020
In which of the following research methods, manipulation and control of variables, and randomization of sample are two of the basic requirements?
- A.
Ex-post facto research
- B.
Descriptive research
- C.
Case study research
- D.
Experimental research
Show answer & explanation
Correct answer: D
Concept
An experiment is the only research design built on two defining controls — the deliberate manipulation of an independent variable and the random allocation of subjects. Manipulation and control of variables let the researcher isolate cause; randomization distributes unknown extraneous factors evenly across groups so that any difference can be attributed to the manipulated variable rather than to pre-existing differences.
Application
The method named here requires (1) manipulation and control of variables and (2) randomization of the sample. Both are simultaneously satisfied only by experimental research: the investigator actively sets the levels of the independent variable, holds extraneous variables constant, and randomly assigns participants to the treatment and control conditions.
Contrast
Methods that merely observe or describe what already exists cannot manipulate a variable, and methods that study a single unit in depth cannot randomize a sample — so they fail one or both requirements.
Result
Experimental research.