OBS Flashcards
What are the main types of observational study?
Analytical observational - cohort studies and case control studies
Descriptive observational studies - ecological, cross sectional and case report studies
What do descriptive studies aim to do?
Describe the distribution of disease and are used to generate hypothesis
What do analytical studies aim to do?
Uncover causes of disease and test hypothesis
What is selection bias and what are some types of selection bias?
Selection bias occurs when the selection of the groups for a study means they cannot be validly compared with eachother.
Sampling bias, responder bias and follow up bias.
What is information bias and what are some types of information bias?
When the way in which data is obtained from different groups differs systematically.
Recall bias, social acceptability bias, recording bias.
What is sampling bias/when does it occur?
When each member of the population does not have an equal chance of being chosen
What is responder bias/when does it occur?
Some people are more likely take part in a study than others so the demographics of the study population doesn’t reflect the general population
What is follow up bias and when does it occur?
When there is a selective loss of follow up in one of the groups
What is recall bias and when does it occur?
when one group has a significantly different level of recall errors than another
All individuals will have SOME recall errors
e.g. those with the disease will have a higher level of recollection about exposure
What is social acceptability bias and when does it occur?
Responders answering questions in a way which they think is socially acceptable and not necessarily true
What is recording bias and when does it occur?
Occurs when there is more information on one group than another e.g. those who are chronically ill will have more medical records
What is interviewer bias and when does it occur?
When the interviewer focusses more on one group and probes one more than the other. Occurs when the interviewer is not blind
What is a confounding factor?
An additional variable which may be responsible for an observed association. This is associated with both exposure and outcome.
What can confounders do ?
Cause false association
Exaggerate association
Mask actual association between exposure and disease
