Bias
refers to interference in a research study which can lead
to misleading results.
One kind of bias is response bias: for example,
patients who know they are being given a drug may often show
improvement -- whether the drug itself is effective or not.
Another kind of bias is observer bias, an
unconscious tendency for experimenters to find the results
they expect. For example, suppose an experiment is conducted
in which a number of patients are divided into two groups
and given either a promising new drug or an inactive placebo
(e.g. a sugar pill). If the experimenter knows which patients
are in each group, he may quite unconsciously notice more
signs of improvement in the drug group than in the placebo
group. This will have the result of making the drug seem more
effective than it really is.
A third kind of bias is selection bias: if
the patients who are assigned to the drug group are less ill
than the patients assigned to the placebo group, then the
drug group will appear to reduce symptoms -- simply because
those patients were less ill to begin with.
A third kind of bias is selection bias:
if the patients who are assigned to the drug group are less
ill than the patients assigned to the placebo group, then
the drug group will appear to reduce symptoms -- simply because
those patients were less ill to begin with.
Further Reading : "Putting
Ginkgo to the Test"
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain
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