1. Relationship Relation: Association: real and spurious Statistical:
Correlation: harmonic
Causation

2. Causation: -direct factor outcome -indirect factor outcome Types of causal relationship: 1- factor is necessary and sufficient (rare), ex.; agent host A outcome

3. 2- factor is necessary but not sufficient: A+B+C outcome 3-factor is not necessary but sufficient: A B C
outcome or or

4. 4- neither necessary nor sufficient: A + B + C
D + E + F
outcome or

5. A B
A + B C
A B + C
A B C
A B
A B
C C

6. Systematic error (bias) Confounders
Before starting to prove causation, We should Identify and evaluate the effects of:
Random Error (chance)
Systematic error (bias)
Confounders

7. Conditions for a relationship to be causal: 1- Strength of the association 2- Temporal relationship 3- Dose response relationship 4- Replication of results 5- Biological plausibility

8. Others: 1- Specificity 2- Consistency 3- Presence of alternative hypothesis 4- Cessation of exposure