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PH 240A: Chapter 11 Alan Hubbard University of California Berkeley (Slides by Nick Jewell)

PH 240A: Chapter 11 Alan Hubbard University of California Berkeley (Slides by Nick Jewell). Pancreatic Cancer by Multiple Levels of Coffee Consumption. Generic Symbols for Entries in 2 x K Table. Overall Test of Association. Overall Test of Association. Population-based & Cohort

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PH 240A: Chapter 11 Alan Hubbard University of California Berkeley (Slides by Nick Jewell)

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  1. PH 240A: Chapter 11 Alan Hubbard University of California Berkeley (Slides by Nick Jewell)

  2. Pancreatic Cancer by Multiple Levels of Coffee Consumption

  3. Generic Symbols for Entries in 2 x K Table

  4. Overall Test of Association

  5. Overall Test of Association • Population-based & Cohort • Case-Control:

  6. Overall Test of Association • Extension of c2 test of association • K-1 degrees of freedom under H0 • Same as standardc2 test of association when K = 2

  7. Coffee Drinking and Pancreatic Cancer 3 d. of f. p = 0.0003 (Pooled c2 = 16.6, p =0.00005)

  8. Test for Trend in Risk • High degree of freedom test low power • Limit set of alternative hypotheses • i.e. risks systematically increase or decrease

  9. Test for Trend: Quantified Exposure Levels Typical HA2 x (2 degrees of freedom) P(D|E=x) x Typical H0 x x x1 x2 x3 xK X, numerical measure of Exposure E

  10. Test for Trend • Weighted linear regression of estimated risks against X • Qualitatively ordered exposure variables • Choose a suitable scale (One d. of f.)

  11. Coffee Drinking and Pancreatic Cancer 1 dof p = 0.0008 2 dof, p = 0.026

  12. Goodness of Fit • How well is variation in risk explained by linear pattern of increase (or decrease) • K-2 degree of freedom test (be cautious about power)

  13. Coffee Drinking and Pancreatic Cancer 1 dof p = 0.0008 2 dof, p = 0.026

  14. Western Collaborative Group Study

  15. WCGS—CHD Incidence against Body Weight Any increasing trend will tend to be detected by the test for trend (based on a linear trend)

  16. Pancreatic Cancer Incidence Against Coffee Drinking Consumption Same graph, but case-control-so use log odds and ignore scale on Y-axis

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