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The Use of 2 by 2 Tables. IN. CAUSAL ASSOCIATIONS. Causality. ASSOCIATION BETWEEN. FACTOR AND HEALTH EVENT. ???. F+. D+. Causality. APPARENT. ASSOCIATION. STATISTICAL. CAUSAL. Epidemiologic Methods. PROSPECTIVE OR COHORT. TIME. F+. D+. F-. D-. Epidemiologic Methods.

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The Use of 2 by 2 Tables

IN

CAUSAL ASSOCIATIONS


Causality

ASSOCIATION BETWEEN

FACTOR AND HEALTH EVENT

???

F+

D+


Causality

APPARENT

ASSOCIATION

STATISTICAL

CAUSAL


Epidemiologic Methods

PROSPECTIVE OR COHORT

TIME

F+

D+

F-

D-


Epidemiologic Methods

TIME

F+

D+

F-

D-

RETROSPECTIVE OR CASE-CONTROL


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)))


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)))




Epidemiologic Methods

TIME

F+

D+

F-

D-

RETROSPECTIVE OR CASE-CONTROL


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)



Causality

STATISTICAL ASSOCIATION

USE OF THE CHI SQUARE

SA

F+

D+


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)


The Use of 2 by 2 Tables

IN

OUTBREAK INVESTIGATIONS


Causality

ASSOCIATION BETWEEN

Food Eaten & Disease (outcome)

???

F+

D+


Epidemiologic Methods

Food-Borne Outbreak

F+

D+

Eaten Risky Food

Outcome Disease

F-

Not Eat Risky Food

D-

OUTCOME NO DISEASE


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)


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