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Bias can also occur in the process of assessment. For example,
patients have been found to report their symptoms differently
to physicians, nurses, and family members. Sometimes this variation
is systematic; for example, health care professionals often underestimate
pain, compared to patient assessments, whereas family members
may overestimate it.
The timing of the assessment
can also produce bias. In retrospective data collection, which
relies on a patient (or, more commonly, a bereaved family member)
making an assessment of past symptom severity, assessment can
be systematically affected by memory failure, or the bereavement
process itself. A comparison of ratings made by the family members
before the death and seven months after bereavement suggested
that family members altered their assessments during bereavement
(Higginson,
Priest, et al., 1994).
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