Bias and Misclassification

Question 1

Bias

Answer 1

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

Question 2

Bias

Answer 2

A source of error for assesing internal validity

Question 3

What can be done to fix a bias

Answer 3

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

Question 4

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

Answer 4

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

Question 5

The direction of a bias

Answer 5

can over or under estimate the true measure of association

Question 6

Information/observation/ measurement related

Answer 6

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

Question 7

Selection related bias

Answer 7

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

Question 8

Selection bias

Answer 8

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

Question 9

Healthy worker bias

Answer 9

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

Question 10

Self-Selection/ Participant (responder) Bias

Answer 10

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

Question 11

Control selection bias

Answer 11

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.

Question 12

Recall Bias

Answer 12

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

Question 13

Hawthorne effect

Answer 13

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

Question 14

Can loss to followup happen in a cohort study?

Answer 14

Yes if it is prosepective

Question 15

Contamination bias

Answer 15

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

Question 16

compliance bias

Answer 16

interventional studies, groups being interventinoally studdied have difference compliences

Question 17

lost to followup bias

Answer 17

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

Question 18

What are selection related biases?

Answer 18

healthy worker biasas, self selection bias, control selection bias

Question 19

What are subject related variation?

Answer 19

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

Question 20

What are observer related variation?

Answer 20

Interviewer, diagnosis/surveillance,

Question 21

interview bias

Answer 21

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

Question 22

diagnosis/surveillance(expectation) bias

Answer 22

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

Question 23

kappa statistic

Answer 23

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

Question 24

Controlling for bias

Answer 24

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

Question 25

ways to control for bias

Answer 25

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

Question 26

Misclassification Bias

Answer 26

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

Question 27

non-differential

Answer 27

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

Question 28

non-differential effect

Answer 28

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

Question 29

Differntial

Answer 29

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

Question 30

differential effect

Answer 30

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

Question 31

I unknowingly misclassified 10 cases of exposure in ONLY the cases

Answer 31

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

Question 32

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

Answer 32

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

Question 33

Misclassified both groups by the same amount

Answer 33

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

Question 34

Controlling for misclassifications

Answer 34

same as information bias

Question 35

Neyman bias

Answer 35

fatal cases being excluded, only looking at the living.

Question 36

Lead-time bias

Answer 36

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

Question 37

length bias

Answer 37

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