important definitions Flashcards
what does error mean?
the difference between an estimated/ measured value and a true value
what does bias mean?
systematic, non-random deviation of results or inferences from the truth, or processes leading to such a deviation
(leaning to one side)
why might error due to selection arise?
sample selection - participation effects mixed with exposure effects
when does diagnostic bias occur?
when diagnosis made on basis of exposure
when might self-selection bias occur?
when subjects make decisions e.g. whether or not to participate
‘healthy worker effect’ = workers self-selecting as more likely to be heathier as remain at work whereas unwell people retire
is participation bias a type of selection bias?
yes
when does misclassification bias occur?
when data is placed into categories
e.g. smokers more likely to be diagnosed with emphysema than non-smokers with emphysema
list some types of information bias
surrogate bias
recall bias
interviewer bias
sample?
small subset of population
population
every member of a group of interest
case
person with a disease of interest
control
person without a disease of interest
randomise
each unit has equal probability of being selected
controlled
compares the results obtained from an experimental sample against a controlled sample
ecological study
counting numbers of people affected in a group
