Frequency association

10 important questions on Frequency association

What is incidence? Prevalence?

new cases occurring during a period of time among a group initially free of disease
Existing cases at a point or period of time.

What are point/period/lifetime prevalence?

Point: People who have the disease in a certain point in time, like a snapshot
period: over a specific period of time
Lifetime: number of individuals who have had a disease in their life, compared to total number of individuals

What is the difference between absolute risk and attributable risk?

Absolute risk- Probability of an event in a population under study(incidence)
Attributable risk- Risk for exposed persons- risk for non-exposed persons. This gives the incidence of a risk attributable to exposure
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When are the RR or OR signigicant?

If the confidence interval overlaps 1, there is no significant risk!

What if the 95% ci for RR/OR is wide?

the estimate is less precise

When is the OR an estimate of RR?

When the incidence of the disease is low

What three main sources of bias?

Selection bias
information bias
confounding
(effect modification)

When is a variable a confounder?

When associated with exposure
Associated with disease
Not part of the causal chain from exposure to disease

What is effect modification?

Interaction, whether the presence or absence of a variable changes the effect of exposure on disease. These can be discovered with multiple(logistic) regression analyses.

How do you calculate R squared?

SSm/SSt

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