Choose one of these stories for your group discussion.

1. What is the individual unit of the study? Each $$i$$ is what?
2. What are $$Y^0$$ and $$Y^1$$ in this study? (Conceptually. Not actual numbers.)
3. What is the treatment ($$D$$)?
4. What causal relationship is stated explicitly or implied by the study?
5. Describe a mechanism that could cause selection bias in the story. Which direction does the bias go?
6. Describe a mechanism that could cause differential effect bias. Which direction does the bias go?
7. Describe what it would mean if the independence assumption was true in this study.
8. Describe how you would do a true randomized experiment to study this causal relationship.

“But, it turns out, some of us prefer to look at and compare ourselves to certain types of individuals: those who make us feel better about ourselves. And that, in turn, can lead to an increase in happiness and life satisfaction.”

“A New, More Rigorous Study Confirms: The More You Use Facebook, the Worse You Feel”

### Study 3: Standing desks

“Standing Up at School Improves Students’ Cognitive Performance, Study Finds”

### Study 4: Activist campaigns on social media

“Specifically, researchers at University of Southern California found viewing viral videos of police shootings and detained immigrants are associated with depressive and PTSD symptoms in adolescents of color.”

### Study 5: Preschoolers’ use of phones and tablets

“The Relation Between Use of Mobile Electronic Devices and Bedtime Resistance, Sleep Duration, and Daytime Sleepiness Among Preschoolers”

### Study 6: Marketing e-mails

“When we analyzed the data from over 5,000 campaigns we found something powerful: campaigns with images had a 42% higher click-through rate than campaigns without images.”

### Study 7: Uber/Lyft and traffic

Warning: This one is conceptually more vague and difficult. “Uber and Lyft are creating more traffic and congestion instead of reducing it, according to a new report” News link: https://www.businessinsider.com/uber-lyft-creating-traffic-cities-bruce-schaller-2018-7