Experimenter (noun)

A person who carries out a scientific experiment or investigation.

Origin:

Late 16th century, from the latin word 'experimentum' meaning a trial, experiment.

Examples:

1. The experimenter measured the reaction time of the participants.
2. The experimenter devised a new method to test the hypothesis.
3. The experimenter recorded the results of the experiment.
4. The experimenter analyzed the data to determine the outcome.
5. The experimenter published the findings of the experiment in a scientific journal.