Which of the following is the best example of a characteristic of an experiment? participants should be selected into the treatment group randomly. participants are rarely aware that they are part of an experiment. participants are observed without researchers making changes to their behaviors. the results of an experiment are based on a questionnaire given to a random sample of the population.

The answer to this question should be: Participants should be selected into the treatment group randomly.

In an experiment, the participant is given an intervention and it hoped to change a parameter. In every experiment, you must ask the participant permission so they must be aware of the experiment. Since this is an experiment, the researcher is allowed to do something that changes the participant behavior as long as it is intentional for the research. The experiment questionnaire should be given to the participant, not the population.
By putting the participant randomly, you can minimize confounding factor from the participant.