Facebook study During the one-week period of January 11–18, 2012, Facebook conducted an experiment to research whether emotional states can be transferred to others via emotional contagion. Facebook users were randomly selected to be part of two parallel studies in which Facebook manipulated the exposure to emotional expressions in the user’s news feed. Two parallel experiments were conducted. In one study, it reduced the positive emotional content; in the other study, the negative emotional content was reduced. For each study, there was a control group (the users’ news feed was not manipulated), and an experimental group (the users’ news feed was manipulated—either positively or negatively). Two variables were measured in each study after the manipulation by Facebook: the percentage of all words produced by a person that was positive and the percentage of all words produced by a person that was negative. There were 689,003 Facebook users in the study. (Source: PNAS, June 17, 2014, vol. 111, no. 24, www.pnas.org/cgi/doi/10.1073/pnas.1320040111)

a. Explain why this study is an experiment.

b. Identity the experimental units.

c. For the study in which exposure to friends’ positive emotional content was reduced, identity the explanatory variable and the two response variables.

d. The Facebook users randomly selected for the study were unaware they were part of this experiment.

Provide a reason Facebook elected not to inform the selected users that they were part of an experiment.

Provide a reason the users selected for the study may have felt not informing them about the study was unethical.