An experiment is conducted where a ruler is dropped with and without music playing, and reaction time is tested. We did not attempt to control for the Placebo Effect in our experiment. Which of the following could have helped us to do this? giving the subject a warning before dropping the ruler

letting the subject move their arm around, rather than holding it still on the table

using more than one subject in the experiment

collecting a third set of data, with the subject listening to a loud talk show

having the experimenter choose the music without any input from the subject

not telling the subject what the expected results are

all of these could have controlled for the Placebo Effect