Questions/Exercises Determine if the following study is observational or experimental. Specify which type of observational or experimental study it seems to be. Explain the reasoning for your choice. In an attempt to study the health effects of air pollution, a group of researchers selected 6 cities in very different environments some from an urban setting (e.g. greater Boston), some from a heavy industrial setting (e.g. eastern Ohio), some from a rural setting (e.g. Wisconsin). Altogether they selected 8000 subjects from the 6 cities, and followed their health for the next 20 years. At this time their health prognoses were compared with measurements of air pollution in the 6 cities. 6 Note: Example 2 is based on a real study which was called, The Six Cities study. The researchers were from the Harvard School of Public Health. Consider the study below and answer follow up questions pertaining to the study. This is another actual study.

Headline: A drug designed to prevent people who are at risk of HIV from being infected is showing promise: a new real-world study found that those who took the drug stayed HIV-free. The finding adds to growing evidence the drug, Pre-exposure prophylaxis (PrEP), serves as an effective method of curbing the spread of the HIV virus.

For the study, the first to look at PrEP, researchers evaluated more than 650 people who began the drug during a 32-month period.Nearly all of the participants were men who have sex with men. Users were more likely than non-users to report that they had multiple sex partners. During the study, participants developed a number of different sexually transmitted diseases but remained free of HIV.

The Food and Drug Administration approved PrEP for use in 2012 and it has since been recommended to groups that engage in sexual practices that place them at increased risk of HIV. The drug can reduce risk of HIV infection by 92% if taken properly, according to the Centers for Disease Control and Prevention (CDC).

Is this an experimental or observational study? Explain. Is enough information in this verbiage given for you to know the full validity of this study? Explain your answer. Did good sampling strategies seem to be used in this study? Explain. Identify a control group and a treatment group if applicable. If not applicable, explain why. Identify variables that may confound this study (aka potential confounding variables).

A study was done to look at the association between obesity and television watching. A simple random sample of people were polled and asked about their height/weight ratio and the number of hours of television the person watches each week. This study will gave insight as to whether obesity and television watching are associated. Is this study observational or experimental? Explain. Name the specific type of observational or experimental study this is and explain your reasoning. What bias may the researcher run into with this study? (think confounding, the way the data was gathered, etc.)