The Use of 2 by 2 Tables

# The Use of 2 by 2 Tables

## The Use of 2 by 2 Tables

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1. The Use of 2 by 2 Tables IN CAUSAL ASSOCIATIONS

2. Causality ASSOCIATION BETWEEN FACTOR AND HEALTH EVENT ??? F+ D+

3. Causality APPARENT ASSOCIATION STATISTICAL CAUSAL

4. Epidemiologic Methods PROSPECTIVE OR COHORT TIME F+ D+ F- D-

5. Epidemiologic Methods TIME F+ D+ F- D- RETROSPECTIVE OR CASE-CONTROL

6. Epidemiologic Methods RISK ANALYSIS THE USE OF THE 2X2 TABLE D+ D- Total IR AR RR a+b F+ a b a/(a+b) F- c d c+d c/(c+d) Tot a+c b+d n (a+c)/n AR= (a/(a+b)-(c/(c+d))) RR= (a/(a+b))/(c/(c+d)))

7. Epidemiologic Methods RISK ANALYSIS (PROSPECTIVE or COHORT) THE USE OF THE 2X2 TABLE D+ D- Total IR a+b F+ a b a/(a+b) F- c d c+d c/(c+d) Tot a+c b+d n (a+c)/n RR(exact)= (a/(a+b))/(c/(c+d)))

8. EXERCISE: CASE Problem #2

9. EXERCISE: CASE Problem #2

10. Epidemiologic Methods TIME F+ D+ F- D- RETROSPECTIVE OR CASE-CONTROL

11. Epidemiologic Methods RISK ANALYSIS THE USE OF THE 2X2 TABLE (RETROSPECTIVE or CASE CONTROL) D+ D- Total IR a+b F+ a b UNKNOWN F- c d c+d Tot a+c b+d n RR(approx)= Odds Ratio=(a*d/c*b)

12. EXERCISE: CASE Problem #2

13. Causality STATISTICAL ASSOCIATION USE OF THE CHI SQUARE SA F+ D+

14. Causality THE 2 by 2 TABLE. STATISTICAL ASSOCIATION Disease Outcome D+ D- NULL HYPOTHESIS F+ a b a+b ALTERNATE HYPOTHESIS Exposure to Risk F- c d c+d Level of sig (a=0.05) a+c b+d n df for 2X2= 1 FOR DECISION Compare ChiSquare calculated ChiSq= (ad-bc)**2n To ChiSquare tabulated (3.84) (a+c)(a+b)(b+d)(c+d)

15. The Use of 2 by 2 Tables IN OUTBREAK INVESTIGATIONS

16. Causality ASSOCIATION BETWEEN Food Eaten & Disease (outcome) ??? F+ D+

17. Epidemiologic Methods Food-Borne Outbreak F+ D+ Eaten Risky Food Outcome Disease F- Not Eat Risky Food D- OUTCOME NO DISEASE

18. Causality THE 2 by 2 TABLE. STATISTICAL ASSOCIATION Disease Outcome D+ D- NULL HYPOTHESIS F+ a b a+b ALTERNATE HYPOTHESIS Exposure to Risk F- c d c+d Level of sig (a=0.05) a+c b+d n df for 2X2= 1 FOR DECISION Compare ChiSquare calculated ChiSq= (ad-bc)**2n To ChiSquare tabulated (3.84) (a+c)(a+b)(b+d)(c+d)