study design and sampling

Question 1

define a descriptive study

Answer 1

describing characteristics of disease in the population without identifying associations or causal inferences

Question 2

define an observational study

Answer 2

an investigation of associations or causal inferences that are occurring in the population without manipulation or intervention from the researcher

Question 3

define an experimental study

Answer 3

researcher intervenes to allocate individuals to treatment or control groups and measures effect

Question 4

what data does a cross sectional study look at

Answer 4

data across a population at a SINGLE POINT IN TIME
can tell the overall PREVALENCE in the population and can compare among different groups
Helps ID risk factors/exposures associated with BEING diseases

Question 5

What can a cross sectional study help you determine?

Answer 5

ASSOCIATIONS!! not causation

Question 6

what is critical in developing a cross-sectional study?

Answer 6

your sampling must be representative of the POPULATION! if you have poor sampling you cannot generalize your results

Question 7

what are advantages of a cross-sectional study?

Answer 7

-relatively cheap and easy
-can look at multiple factors
-good for establishing a baseline
-good beginning step for a new issues
-no lost to follow up or case/control selection bias

Question 8

what are limitations to a cross sectional study?

Answer 8

-least useful for establishing causal relationships
-the prevalence reflects incidence and duration of dz, but may underestimate if sick die or recover rapidly
-impractical for rare dz
-if sampling is poor, results don’t matter

Question 9

How do you select for a case control study

Answer 9

you select cases and control, and sample based on outcome of interest
after, you look back and identify exposures

Question 10

how do you define a case for a case control study

Answer 10

use objective criteria for disease and restrict study to a single disease entity
hard to define with existing cases
restrict to those with potential for exposure
use inclusion or exclusion criteria
consider biases introduced by case definition
try to make group representative of ALL cases

Question 11

what is the point of a control in a case control study

Answer 11

they provide the estimate of exposure rate among the NON-DISEASED
they should be similar to cases, but without disease

Question 12

can you calculate incidence rates from a case control study?

Answer 12

no- you started with identification of prevalent cases

Question 13

what are case control study advantages?

Answer 13

best for rare dz
can be quick
can learn about several potential exposures at the same time
relatively inexpensive