[CH2] BIAS & CONFOUNDERS

Question 1

deviation of outcome measurement

Answer 1

errors

Question 2

errors can be due to

Answer 2

sampling
biological variation
measurement process

Question 3

errors can be eliminated by

Answer 3

larger samples
taking averages of at least 2 measurements

Question 4

systematic induced error which results in under/over estimation of an association

Answer 4

bias

Question 5

bias types

Answer 5

selection bias
information bias

Question 6

selection bias types (5)

Answer 6

volunteer bias
healthy workers effect
neyman’s bias
Berkson bias
attrition bias

Question 7

information bias types (7)

Answer 7

recall bias
reporting bias
interviewer bias
inter-observer bias
intra-observer bias
surveillance bias
detection bias

Question 8

information bias can be controlled by (5)

Answer 8

1-blinding
2-using mail surveys
3-use multiple questions that ask the same important information
4-use multiple sources of information
5-using standard measurement instruments

Question 9

selection bias can be controlled by (4)

Answer 9

1-random selection
2-use of incidence cases in case-control studies
3-avoid use of hospitalized cases from same department of intended disease
4-avoid use of end-stage cases except if they’re the target group

Question 10

effect or association between an exposure & outcome is distorted by presence of 3rd factor related to both

Answer 10

confounder

Question 11

is confounding a bias?

Answer 11

NO

Question 12

characteristics of a confounder

Answer 12

1-must be a risk factor
2-associated w exposure
3-NOT intermediate step in causal path
4-NOT a result of exposure

Question 13

BIAS: prevalence of diseased volunteers is higher than prevalence of diseased individuals in general population

Answer 13

Volunteer bias

Question 14

BIAS: morbidity & mortality from a disease are lower among the sample of those present at work

Answer 14

healthy worker effect

Question 15

BIAS: reflects both risk factors & survivorship

Answer 15

neyman bias (use of prevalent cases in case control studies)

Question 16

BIAS: controls may have increased/decreased exposure to risk factors that leads to their diseases & not the one under study

Answer 16

berkson bias

Question 17

BIAS: loss during follow up

Answer 17

attrition bias

Question 18

BIAS: misinformation due to selective recall of previous activities & exposure

Answer 18

recall bias

Question 19

BIAS: women who had complications during pregnancy recall pregnancy outcomes better than those w/ easier pregnancy experiences

Answer 19

recall bias

Question 20

BIAS: exposures get under-reported because of attitudes/beliefs/perceptions

Answer 20

reporter bias

Question 21

BIAS: drug abuse exposure is under reported due to attitudes & perceptions

Answer 21

reporter bias

Question 22

BIAS: misinformation due to taking sides by interviewers

Answer 22

interviewer bias

Question 23

BIAS: interviewer may ask extra questions, use of voice tone, body language, facial expressions to suggest preference to certain responses

Answer 23

interviewer bias

Question 24

BIAS: variation b/w results obtained by 2+ different observers examining same material

Answer 24

inter-observer bias

Question 25

BIAS: variation b/w results obtained by an observers examining same material more than once

Answer 25

intra-observer bias

Question 26

BIAS: one group is followed up more closely by surveillance system

Answer 26

Surveillance bias

Question 27

BIAS: systematic differences b/w groups due to differences in method of evaluation of outcome

Answer 27

detection bias

Question 28

BIAS: exposed group is evaluated by lab investigations & X-rays while control group is evaluated w/ only an interview

Answer 28

detection bias

Question 29

recall bias is common in

Answer 29

case control studies

Question 30

% of loss that renders a study questionable and in need of sensitivity analysis

Answer 30

more than 20%

Question 31

attrition bias is common in

Answer 31

cohort
clinical trials

Question 31

attrition bias is common in

Answer 31

cohort
clinical trials