Bias and study errors

Question 1

Selection bias

Answer 1

Error in *Recruiting participants

Error in *assigning subjects to a study group resulting in
an unrepresentative sample.

Most commonly a *sampling
bias.

Question 2

Berkson bias

Answer 2

Type of Selection Bias

study population selected from hospital is less healthy than general population

Question 3

Healthy worker effect

Answer 3

Type of Selection Bias

study population is healthier than the general population

Question 4

Non-response bias

Answer 4

Type of Selection Bias

participating subjects differ
from nonrespondents in
meaningful ways

Question 5

Recall bias

Answer 5

Error in *Performing study

Awareness of disorder alters
recall by subjects; common in
retrospective studies

Question 6

Measurement bias

Answer 6

Error in *Performing study

Information is gathered in a
systemically distorted manner

Question 7

Procedure bias

Answer 7

Error in *Performing study

Subjects in different groups are not treated the same.

Question 8

Observer-expectancy bias

Answer 8

Error in *Performing study

Researcher’s belief in the
efficacy of a treatment
changes the outcome of that
treatment

aka *Pygmalion effect; self-fulfilling prophecy

Question 9

Confounding bias

Answer 9

Error in *Interpreting results

When a factor is related to both the exposure and outcome, but not on the causal pathway–>factor distorts or confuses effect of exposure on outcome

Question 10

Lead-time bias

Answer 10

Error in *Interpreting results

Early detection is confused
with INC survival.