Exam 6: Samples and Observational Studies

A 2002 Gallup survey interviewed by phone a random sample of 474,195 U.S. adults. Participants were asked to describe their work status and to report their height and weight (to determine obesity based on a body mass index greater than 30). Gallup found 24.9% obese individuals among those interviewed who were employed (full-time or part-time by choice), compared with 28.6% obese individuals among those interviewed who were unemployed and looking for work. What is the best description of the sample in this study?

On its website, the Washington Post dedicates a page to explaining its survey response rates. A September 2005 monthly political survey contacted 3246 American adults and got complete answers from 1201. What is the approximate 2005 response rate quoted by the Washington Post?

After becoming sick, a patient sees a doctor, who determines the most likely cause is an allergic reaction; the doctor prescribes an antihistamine. The patient returns home and stops burning candles and incense for the next week while taking the medication. By the end of the week, the patient is feeling better and is telling all his friends how wonderful the medication was at relieving his symptoms. What is the best description of this situation?

Sixty-four pregnant women ranked the severity of their heartburn during pregnancy. Researchers rated newborn hair volume using photographs of the newborn's head. They found an association between heartburn severity during pregnancy and the amount of hair on newborns. What can we reasonably conclude from this study?

A study of the occupational exposure to HIV among health care workers recruited 33 health care workers who had become HIV-seropositive after exposure to HIV at work and 665 health care workers who had been exposed to HIV but had not become seropositive. The study found that contaminated health care workers were more likely to have been exposed to large amounts of blood and less likely to have taken the drug AZT immediately after exposure. Which type of study is this?

A study of injuries to in-line skaters used data from the National Electronic Injury Surveillance System, which collects data from a random sample of hospital emergency rooms (ERs). The researchers interviewed 161 people who came to ERs with injuries from in-line skating. The interviews found that 53 people had been wearing wrist guards, and 6 of these people had wrist injuries. Of the 108 people who had not worn wrist guards, 45 had wrist injuries. What is the population that was sampled in this survey?

A researcher is interested in opinions about stem cell research. A random sample of U.S. residents is selected, and the respondents are asked questions about stem cell research. The researcher then compares the responses of men and women in the sample. What is the best description of the overall sample?

The city council in a suburb of Raleigh is interested in the level of public support for a tax increase to support restoration of nearby parks and waterways. A marketing research firm is hired that then selects a simple random sample of 50 adult residents and contacts each to determine whether the resident would be opposed to the tax increase. Of these respondents, 15 indicate that they would be opposed to the tax increase. What is the sample in this example?

A 2012 Gallup survey interviewed by phone a random sample of 474,195 U.S. adults. Participants were asked to describe their work status and to report their height and weight (to determine obesity based on a body mass index greater than 30). Gallup found 24.9% obese individuals among those interviewed who were employed (full-time or part-time by choice), compared with 28.6% obese individuals among those interviewed who were unemployed and looking for work. What can you reasonably conclude from this survey?

In 2001, the Department of Defense funded an ongoing study of current and former service members to evaluate the long-term health effects of military service, including deployments. Almost 150,000 participants have been recruited so far and have agreed to complete one questionnaire every three years. This is an example of

Early life corresponds to the first bacterial colonization of the digestive tract, creating a microbiome thought to play an important role in human development. What might be the effect of early exposure to antibiotics on children's development? One study followed 11,532 full-term babies all born in the county of Avon (United Kingdom) during 1991 and 1992. Exposures to antibiotics during infancy were recorded, along with measures of body mass at regular intervals over several years. The researchers found that antibiotic exposure during the first six months of life was associated with increased body mass later in childhood. What can we reasonably conclude from this study?

A study enrolled 517 children aged 2 to 5 years with a diagnosis of autism spectrum disorder and 315 children of the same age group but without such a diagnosis. The mothers' medical records were examined to see whether they had a metabolic condition (e.g., diabetes, hypertension) during pregnancy. The researchers found that metabolic conditions during pregnancy tended to be more frequent among the mothers of children with autism spectrum disorder than among mothers of control children. What can we reasonably conclude from this study?

The city council in a suburb of Raleigh is interested in the level of public support for a tax increase to support restoration of nearby parks and waterways. A marketing research firm is hired that then selects a simple random sample of 50 adult residents and contacts each to determine whether the resident would be opposed to the tax increase. Of these respondents, 15 indicate that they would be opposed to the tax increase. What is the population of interest?

On its website, the Washington Post dedicates a page to explaining its survey response rates. A September 2005 monthly political survey received complete responses from 1201 American adults, representing approximately a 37% response rate. How many individuals made up the original random sample selected by the Washington Post?