BEHAVIORAL SCIENCE

BIAS

Occurs when one outcome is systematically favored over another. Systematic error.

1)    Selection bias-nonrandom assignment to study group. (e.g.  Berkson’s bias).

2)    Recall bias-knowledge of presence of disorder alters recall by subjects.

3)    Sampling bias-subjects are not representative relative of general population; therefore, results are not generalizable.

4)    Late-look bias-information gathered an inappropriate time-e.g. using a survey to study a fatal disease (only those patients still alive will be able to answer survey).

5)    Procedure bias-subjects in different groups are not treated the same-e.g. more attention is paid to treatment group, stimulating greater compliance.

6)    Confounding bias-occurs with two closely associated factors; the effect of one factor confuses or distorts the effect of the other.

7)    Lead-time bias-early detection confused with increase survival; seem when improved screening (natural history of disease is not changed, but early detection makes it seem as though survival increase).

8)    Pygmalion effect-occurs when a researcher’s belief in the efficacy of a treatment changes the outcome of the treatment.

9)      Hawthorne effect-occurs when the group being studied changes its behavior owing to the knowledge of being studied. 

Ways to reduce bias:

1)    Blind studies (double blind is better).

2)    Placebo responses.

3)    Crossover studies (each subject act as own control)

4)      Randomization.