CAUSAL RELATIONSHIPS
Review Questions
What was Hippocrates known for?
o Father of epidemiology
o Health is impacted by more earthly causes (real world/environment)
o Endemic/epidemic
What was Ignaz Simmelweiss known for?
o Introduced hygienic practices to his clinic
o This drastically changed mortality rates
Who was the Father of modern epidemiology?
o John Snow because he established policy and putting evidence to action
Established systematic way of looking at disease and understanding causation
and putting ideas/thoughts into methods of prevention 8888
Objectives
Define types of causal relationships
Discuss Hill's criteria of Causation
Understand important factors related to disease transmission, such as the epidemiologic triad
Association
Association (Correlation)
o A mathematical link between two variables
o Can be positive or negative
Positive Association (Correlation)
o If the value of one variable increases, the value of the other variable increases as well.
Negative Association (Correlation)
o If the value of one variable increases, the value of the other variable decreases (& vice
versa).
Types of Associations
Spurious
o FALSE Associations (correlation)
o Typically the result of sampling error bias
o When we see there is a mathematical relationship, but its not real
o You can't tell whether its spurious or not;
o Ex: divorce rates and margarine consumption (the less people eat margarine, the less
divorces occur)
Noncausal
o When there is a relationship between two variables, but the relationship is caused by a
third variable
o The more firemen sent to a fire -> the more fire damage occurs
Third variable could be it’s a bigger fire
o Mediated by the third variable that we may not be aware of
Confounders
o An unobserved variable that correlated with both the exposure and outcome variable
Causal Relationship
o When one variable causes a change in another variable
o Real relationship, not accounted by other variables
Ex: as you run faster, the number of calories you burn increases
Review Questions
What was Hippocrates known for?
o Father of epidemiology
o Health is impacted by more earthly causes (real world/environment)
o Endemic/epidemic
What was Ignaz Simmelweiss known for?
o Introduced hygienic practices to his clinic
o This drastically changed mortality rates
Who was the Father of modern epidemiology?
o John Snow because he established policy and putting evidence to action
Established systematic way of looking at disease and understanding causation
and putting ideas/thoughts into methods of prevention 8888
Objectives
Define types of causal relationships
Discuss Hill's criteria of Causation
Understand important factors related to disease transmission, such as the epidemiologic triad
Association
Association (Correlation)
o A mathematical link between two variables
o Can be positive or negative
Positive Association (Correlation)
o If the value of one variable increases, the value of the other variable increases as well.
Negative Association (Correlation)
o If the value of one variable increases, the value of the other variable decreases (& vice
versa).
Types of Associations
Spurious
o FALSE Associations (correlation)
o Typically the result of sampling error bias
o When we see there is a mathematical relationship, but its not real
o You can't tell whether its spurious or not;
o Ex: divorce rates and margarine consumption (the less people eat margarine, the less
divorces occur)
Noncausal
o When there is a relationship between two variables, but the relationship is caused by a
third variable
o The more firemen sent to a fire -> the more fire damage occurs
Third variable could be it’s a bigger fire
o Mediated by the third variable that we may not be aware of
Confounders
o An unobserved variable that correlated with both the exposure and outcome variable
Causal Relationship
o When one variable causes a change in another variable
o Real relationship, not accounted by other variables
Ex: as you run faster, the number of calories you burn increases
