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Perhaps
the most unique feature of the JVIS is its method of scale
construction. Each scale was designed to measure the interest
designated by the scale name and to be relatively unrelated
to other scales. To accomplish this result, careful attention
was paid to the preparation of a large pool of activities.
The ultimate quality and validity of a vocational interest
survey rests on the fidelity to which its constituent activities
reflect the interest or interests in question. In the case
of the JVIS, extraordinary measures were introduced to foster
careful item development and selection. This was followed
by administration of these items to large samples of males
and females, well over a thousand of each. Final activity
selection involved a series of multivariate psychometrically-based
procedures designed to select activities most clearly related
to the interests being assessed, to suppress response biases,
and to minimize the redundancy between scales. From the initial
activity pool of well over 3,000 items, the very best have
been retained for use in the published JVIS.
A
notable feature of JVIS scale construction relates to the
choice of format for the test booklet. The respondent is asked
to indicate a preference between two equally popular interests
rather than simply "like" or "dislike."
While a "like-dislike" format has the appeal of
simplicity, accumulating research has indicated that this
type of format is prone to systematic bias. Individuals may
show a general disposition to respond "like" or
"dislike" rather than express their preference for
the activity described. This results in systematic error (accounting
for as much as a third of the total variance) and poor discrimination
between vocational interest scales. The use of the forced-choice
activity pairing procedure on the JVIS completely eliminates
this source of response bias.
Another
feature of the JVIS is that it places equal emphasis upon
the measurement of interests of women and men. The Survey
was standardized in such a way that an equal number of males
and females contributed to the selection of activities and
scales, and that activities were required to show discrimination
for each sex separately. The format allows males and females
to be measured in terms of a common set of interest dimensions
which do not make discriminations on the basis of traditional
"male" and "female" occupations.
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