ecological studies

Question 1

what do ecological studies do

Answer 1

examine association between outcomes and exposures by using aggregate data

Question 2

aggregate data

Answer 2

time - trend studies

place- geographical studies

Question 3

use of ecological studies

Answer 3

explore quality of care - compare mortality ratio
inequalities in care
generate hypothesis about variation in illness, diagnosis, and response to treatments
correlation between change in disease and risk factors following an intervention
exposures measured over groups or areas

Question 4

data for ecological studies

Answer 4

exposure and outcome at same level of aggregation

routine data - efficient

Question 5

analysis

Answer 5

scattergraphs
linear regression
r = coefficient - strength of association
rsquared - proportion of total variation that can be explained by the regression line

Question 6

source of error

Answer 6

change of definition/coding makes arterfactes

confounding - data not always available

Question 7

strength of ecological study

Answer 7

association in large pop
generate hypothesis
quick and cheap

Question 8

limitations

Answer 8

cannot confirm association at an individual level
costly when exposure data not available
ecological fallacy - assume something about a group that is actually caused by a minority group living in the bigger group