Question

For each of the following, determine whether the statistical study described is an observational study or an experiment. Give a brief explanation of your choice. a. Can choosing the right music make wine taste better? This question was investigated by a researcher at a university in Edinburgh (www.decanter.com/news). Each of 250 volunteers was assigned at random to one of five rooms where they were asked to taste and rate a glass of wine. No music was playing in one of the rooms, and a different style of music was playing in each of the other four rooms. The researcher concluded that cabernet sauvignon is rated more highly when bold music is played than when no music is played. b. The article "Display of Health Risk Behaviors on MySpace by Adolescents" (Archives of Pediatrics and Adolescent Medicine [2009]: 27-34) described a study of 500 publically accessible MySpace web profiles posted by 18-year- olds. The content of each profile was analyzed and the researchers concluded that those who indicated involvement in sports or a hobby were less likely to have references to risky behavior (such as sexual references or references to substance abuse or violence) c. USA Today (January 29,2003 ) reported that in a study of affluent Americans (defined as those with incomes of \(\$ 75,000\) or more per year) \(57 \%\) indicated that they would rather have more time than more money. d. The article "Acupuncture for Bad Backs: Even Sham Therapy Works" (Time, May 12,2009 ) summarized a study conducted by researchers at the Group Health Center for Health Studies in Seattle. In this study, 638 adults with back pain were randomly assigned to one of four groups. People in group 1 received the usual care for back pain. People in group 2 received acupuncture at a set of points tailored specifically for each individual. People in group 3 received acupuncture at a standard set of points typically used in the treatment of back pain. Those in group 4 received fake acupuncture-they were poked with a toothpick at the same set of points used for the people in group 3 . Two notable conclusions from the study were: (1) patients receiving real or fake acupuncture experienced a greater reduction in pain than those receiving usual care; and (2) there was no significant difference in pain reduction between those who received real acupuncture (groups 2 and 3 ) and those who received fake acupuncture toothpick pokes.

Short answer

a. Experimental study, as the researcher is actively manipulating variables to evaluate their impact on the wine taste. b. Observational study, as the researchers are merely observing and analyzing publically available data without manipulating any variables. c. Observational study, as the researchers are analyzing survey results without manipulating any variables. d. Experimental study, as the researcher is manipulating variables (types of treatment) to determine the effect on the outcome (pain reduction).

Step-by-step solution

Case a: Determine the type of research

The first case is concerned with whether the taste of wine can be affected by the kind of music playing in the background. In this study, the researcher varies the type of music played in each room (or no music at all) and measures its effect on the wine taste rating. Therefore, this is an example of an experimental study because the researcher manipulated one variable (music) to see its effect on another (wine taste).

Case b: Determine the type of research

In the second case, the researchers analyze publicly accessible MySpace profiles to draw a conclusion on the relationship between the individual's involvement in sports or hobbies and the display of risky behavior. No variables are manipulated by the researchers; they simply observed and analyzed available data. Consequently, this study is observational.

Case c: Determine the type of research

The third case involves the examination of a survey on affluent Americans' preference for more time over more money. In this case, the researcher is not manipulating any variables, but rather observing and analyzing the results of a survey. This is an example of an observational study.

Case d: Determine the type of research

In the final case, adults with back pain were divided into different groups and each group received a different type of treatment. The researchers then measured the pain reduction each treatment resulted in. In this study, the researchers manipulated the variable (type of treatment) to see how it affects the outcome (pain reduction). Therefore, this is an experimental study.

Key concepts

Experimental Study

An experimental study is a type of research methodology where the investigator intentionally manipulates one or more variables to observe the effect on another variable, typically called the outcome or dependent variable. This manipulation is a crucial aspect as it allows researchers to establish cause-and-effect relationships between variables. Let's take the case of the wine and music experiment from the exercise. Here, the independent variable being manipulated is the type of music, while the dependent variable is the wine taste rating. Random assignment of volunteers to different conditions (music styles) is critical in experimental studies as it helps to ensure that any differences in outcomes are due to the treatment itself and not some other extraneous factors. This strategy minimizes potential biases and increases the study's internal validity.
In experimental research, control groups are often employed, such as the room without music in our example, to compare treatment effects directly. The group with no music serves as a baseline to determine if the types of music actually affect the wine taste rating or if any changes are merely coincidental. Experimental studies are powerful tools in scientific research, as they can offer strong evidence for causal relationships.

Observational Study

An observational study, unlike an experimental study, does not involve intentional manipulation of variables by the researcher. In this type of study, researchers observe and collect data without altering existing conditions or behaviors. The objective is to identify patterns or associations between variables. The MySpace profile analysis mentioned in the exercise is a clear example where researchers examined existing behaviors and preferences as displayed publicly by 18-year-olds. They inferred an association between involvement in sports or hobbies and the likelihood of displaying risky behaviors.
It's important to note that while observational studies can suggest correlations, they cannot definitively establish causation due to potential confounding variables that may not be accounted for. This inherent limitation means that observational studies often need further experimental research to test the hypotheses they generate.

Statistical Analysis

Statistical analysis encompasses a range of techniques used to analyze data and draw conclusions from it. Both experimental and observational studies rely heavily on statistical analysis to interpret the results. For instance, in the wine taste study, statistical methods would assess whether the ratings for cabernet sauvignon are significantly higher when bold music is played compared to no music. Similarly, analyses in the MySpace profile study might include chi-square tests to determine whether the observed association between hobbies and risk behavior display is statistically significant.
Statistical analysis not only helps to confirm or refute the hypotheses but also provides an estimate of the reliability of the findings, often through measures such as confidence intervals and p-values. Properly conducted, statistical analysis offers a robust framework for translating raw data into meaningful insights, despite the complexities and potential uncertainties inherent in research data.

Random Assignment

Random assignment is a fundamental concept in experimental research design. It is the process of assigning study participants to different groups or conditions in a way that is entirely random. This randomization is key in ensuring that each group is comparable before any treatments are applied. By doing so, it helps eliminate selection biases and equalizes other variables across the groups that could otherwise influence the outcome.
In our exercise, the back pain study involved random assignment of adults into four distinct treatment groups, including a group receiving sham acupuncture. This approach strengthens the validity of the conclusion that real or sham acupuncture had a greater effect on pain reduction than usual care. It offers convincing evidence implying that the observed results are attributable to the treatments themselves and not to some pre-existing differences among participants. Random assignment is a cornerstone of control within experiments, and its proper application is crucial for the credibility of experimental results.