Two approaches to removing confounds

Example of Spurious Correlation: Ice Cream Sales and Crime Rates

Analyzing a Research Finding

Interpreting Correlational Research

Between-Subjects Experiment

Example of a Confounding Variable: Mood and Memory

Causal Limitations of Quasi-Experimental Research

What type of variable is an extraneous factor that differs on average across levels of the independent variable, providing a plausible alternative explanation for any observed difference?

A researcher conducts a study to see if drinking caffeinated coffee improves memory performance. Participants in the 'Caffeine' group drink coffee in a warm, quiet cafe, while those in the 'Decaf' group drink coffee in a noisy, cold laboratory. Match each element of this study to its corresponding variable role.

A researcher investigates whether a new herbal supplement improves sleep quality. She gives the supplement to a group of participants who also practice daily meditation, while the control group receives a placebo and does not meditate. In this study, the practice of meditation is a confounding variable.

Arrange the logical steps a researcher takes to analyze how an extra factor becomes a confounding variable that invalidates the causal conclusions of an experiment.

A researcher concludes that a new 'morning exercise' routine improves worker productivity; however, the group assigned to the exercise routine was tested at 9:00 AM, while the control group was tested at 3:00 PM. When evaluating the validity of the researcher's causal conclusion, the 'time of day' must be recognized as a ________ variable because it varies systematically with the independent variable and offers a plausible alternative explanation for the results.

Any extraneous variable present in an experiment is automatically classified as a confounding variable.

Which statement best explains the difference between a 'simple' extraneous variable and a 'confounding' variable in an experiment?

Match each research scenario to the extraneous variable that functions as a confounding variable in that study.

A researcher studying the effect of sleep deprivation on reaction time notices that participants in the sleep-deprived condition consumed, on average, far more caffeine than participants in the well-rested condition. To classify caffeine as a confounding variable rather than a mere extraneous variable, the researcher must confirm that caffeine consumption _____ across the two experimental conditions.

A peer reviewer is evaluating whether a study's causal conclusion is compromised by a confounding variable. Arrange the following evaluative steps in the order a careful reviewer should apply them.

Based on the definition of a confounding variable in psychological research, define what a confounding variable is. In your answer, explain how it behaves in relation to the independent variable and describe the primary scientific challenge it introduces when researchers attempt to establish a cause-and-effect relationship.

In the context of this study, identify the independent variable, the dependent variable, and the confounding variable. Explain how the confounding variable behaves systematically in relation to the independent variable, and explain why this prevents the researcher from drawing a clear cause-and-effect conclusion about the app's effectiveness.

A cognitive psychologist runs an experiment to test the effect of background noise (classical music vs. silence) on memory recall. Participants in the music condition are tested in a warm, comfortable room with soft lighting, whereas participants in the silent condition are tested in a cold, uncomfortable room with harsh fluorescent lighting. Apply the concept of a confounding variable to this scenario to identify the confounder, explain how it systematically co-varies with the independent variable, and describe the threat it poses to the study's validity.