Exam 5: Causation: Can We Say What Caused the Effect

A study published in 2007 by Christopher Johnson, Professor of Music Education and Music Therapy at the University of Kansas, revealed that students in elementary schools with superior music education programs scored around 20 percent higher in math scores on standardized tests, compared to schools with low-quality music programs. Is this an observational study or a randomized experiment?

Recently, a Montana newspaper asked people to go to their website and respond yes or no to the question: "Should federal protections on grizzly bears be lifted?" Of 933 opinions, 58.1% said "Yes", and 41.9% said either "No" Or "Uncertain". Is it valid to conclude from the poll that over half of all Montana residents favor lifting the protections?

Babies born with low birth weights (less than 2500 grams) are at an increased risk for many infant diseases. Researchers in North Carolina collected data to see what variables may influence the birth weight (in grams) of a child, including whether the mother drank alcohol during pregnancy, whether the mother smoked during pregnancy, the mother's age (years), the gestation of the pregnancy (number of weeks from conception until birth), the mother's race, the length of the birth (hours), and several others. The following plot was created to summarize some of the data collected. -Explain why whether the mother drank alcohol during pregnancy is a confounding variable when trying to determine if smoking increases the risk of low birth weight.

A Pew Research Center poll randomly selected and surveyed 2,002 US adults in the 25-32 age group and asked about their annual income. They found strong evidence that the unemployment rate for people without a college degree was higher than the unemployment rate of those with a college degree. Can the researchers conclude that college is the cause of the decrease in unemployment among 25-32 year old U.S. adults?

Researchers randomly assigned patients with severe acne to one of two treatments: the standard topical antibiotic (our control) or a new antibiotic taken orally (the treatment). Six months later an evaluation of skin problems was made by a doctor who did not know which medication subjects had been given. What is the primary advantage of random assignment of the treatment?

The following table shows the responses from a sample of 680 people in the General Social Survey to the question, "Do you sometimes drink more than you think you should?" -What proportion of males responded that they drink more than they should?

January 22, 2016, NPR news headline reads "Why Poverty May Be More Relevant Than Race For Childhood Obesity." The article states, "At first glance it looked like childhood obesity was more common among African Americans or Hispanics... When they accounted for poverty, though, the trend vanished." The study collected data on a random sample of K-12 students in Massachusetts. Does this study design allow us to generalize results to the population of all Massachusetts K-12 students?

A matched pairs design will have less variability in the differences in mean response between two groups than a completely randomized design.

A study published in 2007 by Christopher Johnson, professor of music education and music therapy at the University of Kansas, revealed that students in elementary schools who took private music lessons scored around 20 percent higher in math scores on standardized tests, compared to students who did not take private music lessons. -What is the explanatory variable?

In a study on treatments for anorexia, researchers recruited 30 teenage girls with anorexia. The girls were ranked by weight prior to the study. Of the heaviest three girls, one was randomly assigned to a "family" therapy, one to a "cognitive/behavioral" therapy, and one to a control group. The same was done for the next three heaviest girls, down to the three lightest girls. After five weeks of treatment, researchers weighed the participants. Researchers would like to determine which, if any, of the treatments are most effective in treating anorexia. -Can the results from this study be generalized to the population of all teenage girls with anorexia?