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Cause and Effect in Studies: Smoking and Lung Cancer

Explore the significance of prospective and retrospective studies in determining causation, common design flaws, and the importance of critical analysis in research. Gain insights from the smoking and lung cancer case study.

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Cause and Effect in Studies: Smoking and Lung Cancer

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Presentation Transcript

  1. Experimental Design Group 2: Nabilah, Jing Kai, Soon Guan

  2. Prospective Study vs Retrospective Study • Flaws in Studies • Cause and Effect • Case Study: Smoking and Lung Cancer • Conclusion Outline Experimental Design

  3. Reading Salsburg, David (2001). The Lady Tasting Tea: How Statistics Revolutionized Science in the Twentieth Century, W.H. Freeman (Chapter 18, Does smoking cause lung cancer?)

  4. Prospective Study • Subjects are selected and monitored over a period of time for development of disease Problems: • Extrapolation issues • Time consuming

  5. Retrospective Study • Subjects with disease are identified • Investigations for prior conditions associated with disease Problems: • Rare diseases

  6. Flaws in Studies • Every study has its flaws • Non-random samples → Reinforcement of results through consistency over many studies

  7. Correlation Does Not Imply Causation!

  8. Cause and Effect: A implies B = Not A implies not B

  9. Postulates for Causation • Whenever the agent can be cultured, the disease is there • Whenever the disease is not there, the agent can’t be cultured • When the agent is removed, the disease goes away

  10. Does Smoking Cause Lung Cancer? Case Study

  11. Overview • Prospective & retrospective studies done • Widely reported that smoking causes lung cancer

  12. However...

  13. Postulates not met • Flaws in experimental design • Publication bias (Fisher, 1958) • Confounders Eg. Genetics

  14. Conclusion • Correlation does not imply causation • Not easy to determine cause and effect • Studies are still important as they can still give an idea and provide clues on the possible underlying causes of a disease

  15. Thank You!

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