Health Science Midterm #2
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Define volunteer bias.
when participants who volunteer for a study, differ in some systematic manner compared to those who do not participate
What might cause volunteer bias? (4)
- healthier than non-responders
- more interested in research
- gender differences
What is a selection bias in literature reviews?
language bias: when the sample of papers included in the review excludes studies published in a language other than English
What can we do to fix selection bias (systematic error) (2)?
- use statistical techniques
- different study design
Define information bias.
Introduced when information about the study participants is incorrect.
What are the three sources of information bias?
- interviewer bias
- misclassification of exposure
- misclassification of outcome
What is interviewer bias?
introduced by the way in which study interviewers collect data on study participants
What is an example of interviewer bias?
an interviewer may obtain information that supports a certain hypothesis
What causes interviewer bias?
may be caused by knowledge of the study hypothesis
How can you avoid interviewer bias?
- masking interviewers to the outcome or exposure status
- mask interviewers to the study hypothesis
- standardized questionnaires consisting of close ended questions
- training interviewers
What is reporting bias?
participants "collaborate" with interviewers to provide responses that they think the interviewers wants to hear
Define social desirability bias. Give an example.
- providing socially desirable responses
- example: under reporting weekly alcohol intake
What are some things people under-report? (4)
- sexual behaviour
- alcohol consumption
- drug use
How do we minimize selection bias? (3)
- study design
- eligibility criteria
- sample selection
How do we minimize information bias? (2)
- Use standardize tools to elicit information
- blind interviewers and participants to the study hypothesis
How do you select people in case control studies?
select people who have the disease of interest (cases) AND people who do not (controls)
How does case control studies measure the level of exposure in each group?
measures retrospectively (from past events)
What would you like to do?
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