Through which research method is the manipulation of an independent variable and its effect on a dependent variable examined, with reference to a hypothesis, under controlled conditions?

Manipulating an independent variable and testing its effect on a dependent variable under control against a hypothesis is experimental research.

Ex post facto research studies effects after the cause has occurred.

Descriptive research portrays conditions without manipulation.

Case study research examines a single unit in depth.

Only the experiment manipulates a factor under controlled conditions.

Random assignment and a control group strengthen its causal inference.