Bias

Question 1

When does bias occur?

Answer 1

When there’s a systematic error or favor in a particular direction

Question 2

Selection bias

Answer 2

Nonrandom assignment to participation in a study group

Question 3

Recall bias

Answer 3

Knowledge of presence of disorder alters recall by subjects

Question 4

Sampling bias

Answer 4

Subjects are not representative of the general population, making the results not generalizable

Question 5

Sampling bias is a type of what other bias?

Answer 5

Selection bias

Question 6

Late-look bias

Answer 6

Information gathered at an inappropriate time

Question 7

Procedure bias

Answer 7

Subjects in different groups are not treated the same

Question 8

Confounding bias

Answer 8

Occurs when factor is related to both exposure and outcome, but is not on the causal pathway.
The factor distorts or confuses effect of exposure on outcome.

Question 9

Lead-time bias

Answer 9

Early detection confused with increased survival

Question 10

Observer-expectancy effect

Answer 10

Occurs when a researcher’s belied in the efficacy of a treatment changes the outcome of that treatment

Question 11

Hawthorne effect

Answer 11

Occurs when the group being studied changes its behavior owing to the knowledge of being studied

Question 12

What are Berkson’s bias and loss to follow-up examples of?

Answer 12

Selection bias

Question 13

Where is recall bias common?

Answer 13

retrospective studies

Question 14

What type of bias is this an example of: using a survey to study a fatal disease

Answer 14

Late-look bias. Because only those patients alive will be able to answer the survey.

Question 15

What type of bias is this an example of: More attention is paid to treatment group, stimulating greater adherence

Answer 15

Procedure bias

Question 16

What type of bias is seen with improved screening?

Answer 16

Lead time bias (natural history of disease isn’t changed, but early detection makes it seem as though survival increases)

Question 17

What’s a crossover study? What type of bias can it help limit?

Answer 17

Where each subject acts as own control. Confounding bias.

Question 18

What types of bias can randomization help with?

Answer 18

Selection and confounding bias

Question 19

What can matching help with?

Answer 19

Confounding bias

Question 20

2 general ways to limit bias?

Answer 20

Blind studies: limit influence of participants and researchers on interpretation of outcomes.
Placebo control groups