Bias and Misclassification Flashcards Preview

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Flashcards in Bias and Misclassification Deck (37)
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1
Q

Bias

A

A systematic ( non-random) error in study design or conduct leading to errounous results….distorts the relationship btw exposure and outcome

2
Q

Bias

A

A source of error for assesing internal validity

3
Q

What can be done to fix a bias

A

Nothing after the study has ended, bc it has already occured. ANy consideration must be done before hand.

4
Q

What 3 components do researchers look for when assesing for a bias?

A

Sourse, type… magnitude, strength… direction

for magnitutde can account entirely for wk association, but not likely to acount for entire very strong association… Large OR/RR

5
Q

The direction of a bias

A

can over or under estimate the true measure of association

6
Q

Information/observation/ measurement related

A

Any aspect in the way the researcher collects inforamtion or measure/observes subject which creates systematic differences btw groups in the quality/accuracy of their information

7
Q

Selection related bias

A

any aspect in the way the reasearcher selects subjects which creates a systemeat difference in the composition btw groups…. not reprenting the full population… P value tell if groups are equal

8
Q

Selection bias

A

Selecting study subjects that are not representative of your primary population of interest or that generates differences in groups being compared

9
Q

Healthy worker bias

A

can easily be seen in prospective cohort studies… workers usually exhibit lower overall death rates than the general pop bc severly ill and disablesd ppl ar eexcluded form employment

10
Q

Self-Selection/ Participant (responder) Bias

A

those that wish to participate(volunteer) may be differnt in some way to those that don’t bolunteer or self-select(refusal/non repsonse) to partcipate

11
Q

Control selection bias

A

can easily be see in case control studies

It’s hard to find controls. they have to be as close as possible without ever having disease.

12
Q

Recall Bias

A

A differential level of accuracy in provided information btw study groups. People who have had a bad experience have a much clearer memory of detail

13
Q

Hawthorne effect

A

The nobelty of being research subjects and the increased attention from such coudl lead to temporary increases in study examples responses

14
Q

Can loss to followup happen in a cohort study?

A

Yes if it is prosepective

15
Q

Contamination bias

A

interventional study…. members of the control gourp accidently or outside of the study protocol receive the treatemnt or are exposed to the intervention being studided

16
Q

compliance bias

A

interventional studies, groups being interventinoally studdied have difference compliences

17
Q

lost to followup bias

A

groups being studied have different withdrawal or lost to followup rates or there are other differences btw those that stay in the study and those that withdraw or are lost to fllow up
differential vs not differential

18
Q

What are selection related biases?

A

healthy worker biasas, self selection bias, control selection bias

19
Q

What are subject related variation?

A

Recall, contamination bias, complaince bias, lost to followup bias,

20
Q

What are observer related variation?

A

Interviewer, diagnosis/surveillance,

21
Q

interview bias

A

a systematic difference in soliciting, recording or interpreting on the part of the reasearcher, interviewers knowledge may influence response, and not apply equally btw groups. why a double blind study is good

22
Q

diagnosis/surveillance(expectation) bias

A

different evaluation/classification/diagnosis/observation btw study groups. observer may have preconceived expectiations of what they should find… hawthorne like effect for researchers perspective

23
Q

kappa statistic

A

allows statistics to be done on evaluators to see if there is any differene btw them.

24
Q

Controlling for bias

A

Select most precise, accurate, medically-appropriate measures of assessment and evalution/observation… used published and past utilized techniques and process if possible

25
Q

ways to control for bias

A

blinding/masking, randomly allocate observers/interviewers for data collection, build in as many methods necessart ro minimize loss to followup, start with more people then needed for loss to follwo up

26
Q

Misclassification Bias

A

error in classifying either disease or exposure status or both… putting ppl in the wrong box

27
Q

non-differential

A

error in both groups equal…. Misclassification of exposure or disease which is unrelated to the other, depending on study design

28
Q

non-differential effect

A

For dichotomous 2 category variables, bias can move the measure of association TOWARD THE NULL HYPOTHESIS….. MOVES IT TOWARD 1.0… conservatie error

29
Q

Differntial

A

misclassification of exposure or disease is related to the other, depending on study design

30
Q

differential effect

A

bias can move the measure of association IN EITHER direction… it can inflate or attenuate your effect… differntial is related to the opposite element

31
Q

I unknowingly misclassified 10 cases of exposure in ONLY the cases

A

this is differential, bc it only effected the one side,

32
Q

There is a misclassification on both sides, but not in equal amounts. 10% on one side, 40% on other

A

this is differential, bc they are not balanced… still shifting the measurements unequally

33
Q

Misclassified both groups by the same amount

A

non differential… pushes the OR towards nutrality, and more likely for us to say there is no difference so the error is conservative and less painful

34
Q

Controlling for misclassifications

A

same as information bias

35
Q

Neyman bias

A

fatal cases being excluded, only looking at the living.

36
Q

Lead-time bias

A

amount of time a person has to see the disease present, cancer vs strep throat

37
Q

length bias

A