In Exercises 21–28, determine whether the study is an experiment or an observational study, and then identify a major problem with the study.
Drinking and Driving A researcher for a consortium of insurance companies plans to test for the effects of drinking on driving ability by randomly selecting 1000 drivers and then randomly assigning them to two groups: One group of 500 will drive in New York City after no alcohol consumption, and the second group will drive in New York City after consuming three shots of Jim Beam bourbon whiskey.

Verified step by step guidance

1. Identify the type of study: Determine if the study involves manipulation of variables or merely observation. In this case, the researcher is assigning participants to different conditions (alcohol consumption vs. no alcohol consumption), which indicates an experiment.
2. Define the independent and dependent variables: The independent variable is the alcohol consumption (no alcohol vs. three shots of whiskey), and the dependent variable is the driving ability.
3. Consider ethical implications: Evaluate whether the study design poses any ethical concerns, such as the safety of participants and others, given that driving under the influence is illegal and dangerous.
4. Assess the validity of the study: Consider if the study design allows for a valid conclusion about the effect of alcohol on driving ability. The random assignment helps control for confounding variables, but ethical concerns may invalidate the study.
5. Identify a major problem: The primary issue with this study is the ethical concern of having participants drive under the influence, which poses significant risks to their safety and the safety of others.

Key Concepts

Experimental Study

An experimental study involves the manipulation of one or more independent variables to observe the effect on a dependent variable. In this context, the researcher assigns participants to different conditions (sober vs. intoxicated driving) to directly assess the impact of alcohol on driving ability. This design allows for causal inferences about the relationship between drinking and driving performance.

Observational Study

An observational study, in contrast, does not involve manipulation of variables; instead, researchers observe and measure outcomes without intervention. This type of study is useful for identifying correlations but cannot establish causation. Understanding the difference is crucial for evaluating the validity of the research findings in the context of the question.

Random Assignment

Random assignment is a technique used in experimental studies to ensure that each participant has an equal chance of being assigned to any group. This process helps eliminate bias and confounding variables, making the groups comparable. In the given study, random assignment is employed to divide drivers into sober and intoxicated groups, which strengthens the reliability of the results.