Consider the following causal question:

• What is the impact of stay-at-home orders due to COVID-19 on economic activity in a state?

For above question address the following issues

1. What is the outcome variable of interest and how would you characterize the "treatment"?
2. 2Indicate plausible sources of selection or omitted-variable bias that led you to believe that direct comparisons of outcomes from observational data would not yield a good measure of the causal effect