Epidemiology: Key concepts Flashcards
Meaningful mortality rate statistics need what?
A denominator population (how many people) and a time frame
What is a denominator and name some examples?
- It is where the deaths have happened. Examples include:
- Health board,
- City,
- Hospital,
- Disease register,
- Recruited to a study
Name some examples of observational studys
Case series, cross sectional study, cohort study and case controlled study.
What is a case series?
A series pf cases with the same disease
What is a population case-series (ecological studies)
Unit of study is a whole population, and these are useful to study signs and symptoms and look for causal hypotheses.
What is standardisation?
A set of techniques based on weighted averaging used to remove the effects of differences in age or other confounding variables when comparing two populations.
What are some of the limitations of ‘crude’ rates?
They are of limited value when comparing two populations with different structures because of confounding variables.
What are the methods of direct and indirect standardisation?
Direct - Using known age-specific mortality rates to standardise.
Indirect - Using a reference population when the age-specific mortality rates are unknown to standardise
What is the SMR?
The standard mortality rate. Compares the number of deaths to the number of expected deaths.
What is a confounding variable?
A third variable that also has an effect on your dependent variable.
What are two methods of dealing with a confounding?
Study design and data analysis (standardisation)
What is mean’t by confounding?
Confounding is the distortion of the association between an exposure and health outcome by an extraneous, third variable called a confounder.
What is bias?
An error in the conception and design of a study leading to results or conclusions that are systematically different from the truth.
Describe how systematic errors can occur
In what data is collected, how the data is collected, analysed, interpreted or reported.
Bias can lead to wrong conclusions about?
Disease causation and treatment effectiveness