Homework 2

Problems

Complete each of the following problems. Submit your solutions — stapled — at the beginning of class on Wednesday.

Problem 1: Read the abstracts for each of the linked journal articles. For each study, determine whether the study is observational or experimental. Explain your decision. For each study that is observational, does the result imply the causal story ''\(X\) causes \(Y\)''? Explain.

  1. Happy People Have Children: Choice and Self-Selection into Parenthood
  2. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet
  3. The effect of physical activity on mortality and cardiovascular disease in 130,000 people from 17 high-income, middle-income, and low-income countries: the PURE study
  4. Graduate Student Mental Health: Lessons from American Economics Departments
  5. A Randomized Effectiveness Trial of Brief Cognitive-Behavioral Therapy for Depressed Adolescents Receiving Antidepressant Medication

Problem 2: For each of the following associations, propose a possible confounder that could explain the observed association.

  1. Children with larger shoe sizes are scored as having better reading ability.
  2. Accounting for age (i.e. comparing individuals of the same age), taller men tend to have higher IQs than shorter men.
  3. Crime rate and ice cream sales are associated over time, with the highest crime rates tending to occur during peak ice cream sales.
  4. Mortality rate is inversely associated with coffee consumption.

Problem 3: Construct a rug plot, histogram, and boxplot by hand (not using R) for the following two data sets. Choose the left-endpoint of the left-most bin to be a reasonable integer, and use at least 3 integer-width bins.

  1. -0.98, -2.82, -0.05, 1.39, -4.69, 4.97, -4.66, 2.05, -2.60, 1.57
  2. 0.43, 2.76, -2.20, 3.19, 4.57, -0.95, 4.03, -2.37, 2.72, -0.57, -0.30