what is the purpose of the descriptive study?
identify and count cases of the disease in the population according to person, place, and time, and conduct sample studies
what is a case report? case series?
- case report: report on 1 patient
- case series: report on a group of people
what are case report and series are useful for? limitations?
useful for:
- recognition and description of new diseases, new manifestations of a disease
- detection of drug side effects
- provide insight into disease mechanisms
- provide info to help create a hypothesis
limitations
- no explicit comparison groups
what are ecological studies?
- a study that examines rates and disease about a population-level factor
- a unit of observation is the group (country, state, neighborhood) rather than the individual
- exposure and outcome data at group level
what P-value is significant?
</= 0.05
what are the limitations of ecological studies?
- can’t adjust for confounding factors (can not account for other factors)
- complex relationships can be masked
- ecological fallacy: group level associations may not transfer to the individual level
- issues with suing prevalent cases: prevalence is not ideal of Etiological research because it combines incidence and duration
what are the strengths of ecological studies?
- inexpensive and fast - conducted on available data
- good for the early stage of knowledge
- a wider range of exposures (especially for international studies) than other types of studies
- might want to study the ecological relationship
- analysis is easy using a creation coefficient (r) or linear regression
what are cross-sectional studies and surveys?
- a study/survey that examines the relationship between an exposure and disease at a single point in time
- takes a snapshot
- measures exposure prevalence in relation to disease prevalence
- many surveys are cross-sectional
what are the limitations of cross-sectional surveys?
- problem with inferring temporal sequence of exposure and outcome (which came first)
- problematic when exposure is a changeable characteristic (smoking)
-prevalent cases tend to be cases of longer duration which might e biased
strengths of the cross-sectional survey? when is it fine for exposure to be a characteristic?
- quick and inexpensive
- highly generalized if based on general pop (gov surveys)
- problem with temporal inference can be avoided for inalterable, long-term and historical exposures
- fine for immutable characteristics (genetic testing/blood type), measures of long-term exposure (lead in bone), and historical exposure (activity over past 30 years
what is the purpose for analytic cases?
compare groups and systematically determine if there is a comparison
define crude?
rates or risk based on raw data `
crude all-cause mortality rate
the total number of deaths from all causes per 100,000 pop
direct standardization
- limitation of trying to compare crude rates—calculated for different populations—directly is that the
populations may differ in structure by other factors such as age. A method that allows researchers to
compare different populations that differ by factors such as age
