Question

activity 4 of 6: placebo
angry facial expressions
a clinical research firm believes that seeing an angry facial expression can cause a rise in the viewers blood pressure. to test this hypothesis, researchers gather two groups, each with one hundred people; fifty men and fifty women. each group is hooked up to
which of the following choices best identifies the placebo of this experiment?
the series of pictures with neutral expressions
the machines monitoring vital statistics
the series of pictures with angry expressions
the blood pressure of the test subjects

Explanation:

A placebo is a substance or treatment with no therapeutic effect, used as a control in an experiment. In this case, the neutral - expression pictures act as a control to compare the effect of angry - expression pictures on blood pressure. The machines are for measurement, angry - expression pictures are the treatment being tested, and blood pressure is the measured variable.

Answer:

the series of pictures with neutral expressions