References for Causation and Study Design
Curated resources to deepen your understanding of causation, confounding, and the differences between observational studies and experiments.
Wikipedia Articles
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Correlation does not imply causation - Wikipedia - Classic explanation of why statistical association between variables does not prove that one causes the other, with memorable examples.
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Confounding - Wikipedia - Detailed coverage of confounding variables, how they distort apparent relationships, and methods researchers use to control for them.
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Simpson's paradox - Wikipedia - Explains how trends appearing in subgroups can reverse when data is combined, with famous real-world examples from medicine and admissions.
Textbooks
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The Practice of Statistics by Starnes, Tabor, Yates, and Moore - W.H. Freeman (2018) - Thorough coverage of observational studies versus experiments, random assignment, and establishing causation for the AP exam.
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Statistics Through Applications by Yates, Moore, and Starnes - W.H. Freeman (2008) - Accessible introduction to study design with real-world case studies showing how confounding affects research conclusions.
Online Resources
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Experiments vs Observational Studies - Khan Academy - Clear video explanations of the difference between study types and why only experiments with randomization can establish causation.
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Causal Inference in Statistics: A Primer - Judea Pearl (online excerpts) - Introduction to modern thinking about causation, including causal diagrams that help visualize confounding relationships.
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Understanding Simpson's Paradox - Brilliant.org - Interactive lessons walking through examples of Simpson's Paradox and how to recognize when aggregated data might be misleading.
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Randomized Controlled Trials Explained - NIH National Library of Medicine - Overview of how medical researchers design experiments to establish whether treatments actually work.
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AP Statistics: Data Collection - College Board - Official course framework and sample questions covering observational studies, experiments, and confounding for exam preparation.