A researcher conducted three experiments with 100 subjects each, following a uniform design, instead of one experiment with 300 subjects. This is known as

Repeating the same experimental design on separate groups of subjects is replication, a check on whether findings recur.

Manipulation is the deliberate control of an independent variable, not the act of rerunning a study.

Observation is watching and recording behaviour without necessarily repeating a whole design.

Validation concerns whether a measure or study actually captures what it claims, a different concern.

Splitting three hundred subjects into three trials of hundred lets the researcher confirm consistency of results.

Successful replication strengthens the reliability and external validity of a conclusion.