Page 293 - Encyclopedia of Nursing Research

260 n InSTRUMenTaTIon

instrument’s ability to finely discriminate in measureable. Item generation involves deci-
individual differences and changes in the sions about concept dimensionality and scal-
I concept under study. Reduction of measure- ing methodology.
ment error is achieved by assuring that as When the phenomenon of interest is a
much response variability as possible is due highly abstract concept, the theoretical def-
to the subject’s relationship to the concept inition will include a number of conceptual
under study rather than to inconsistent or aspects that require measurement. Less
systematic extraneous factors. abstract concepts can often be indexed with
The term psychometrics refers to the test- items that tap only one or more finite aspects.
ing of self-report measures and to the sta- For each aspect of the concept, items must be
tistics that are utilized in that examination. developed in a manner that assures homo-
Self-report measures generally fall into the geneity within that conceptual dimension.
categories of norm-referenced and criterion- Thus, the instrument may have to be multi-
referenced. With norm-referenced instru- dimensional or unidimensional, depending
ments, the goal is to obtain a spread of scores on the concept of interest. Typically, multidi-
across a wide range for the purpose of dis- mensional concepts will be measured with
criminating between subjects. Criterion- instruments that have a subscale that relates
referenced measures are constructed for the to each dimension.
purpose of determining whether a subject Decisions about scaling involve whether
has or has not achieved a predetermined set the model is meant to scale stimuli or people.
of target behaviors. Steps in instrumenta- Methods used for scaling stimuli are paired
tion for these two categories differ: however, comparisons, constant stimuli, successive
the majority of attitudinal and behavioral categories, and psychophysical methods.
measures applicable to nursing are norm- Common approaches to scaling people are
referenced, and their construction and test- cumulative (e.g., Guttman-type), differential
ing is emphasized. (e.g., Thurstone-like), and summated (e.g.,
Instrumentation for self-report measures Likert-type) instruments. nunally (1978) pro-
involves three general phases: development, vided an excellent overview of these scaling
testing, and revision. Instrument develop- procedures. other decisions in item-gener-
ment involves concept clarification, develop- ation include factors involved with instru-
ing a theoretical definition, operationalizing ment formatting. These factors relate to levels
the concept, and generating items. Concept of measurement, scaling responses, and the
clarification commonly is done through appearance of the scale to the respondent.
concept analysis, synthesis, or derivation. Instrument testing for self-report mea-
Concept analysis involves a careful review sures involves two aspects. Initially, the con-
of literature with attention to consistencies tent of the instrument is examined to assure
and inconsistencies in the use of the concept. its relationship to the theoretical definition
Concept synthesis uses clinical observa- of the concept. The procedures include esti-
tions to explore the phenomenon of interest. mates of whether the concept has been suf-
Concept derivation consists of moving a con- ficiently indexed by the instrument’s items
cept from one field or discipline to another. and whether the format is clear and promotes
after the concept to be measured is clarified, response consistency. evaluation of the link
a theoretical definition is formulated that between the concept and items is primarily
delineates the dimensions of the concept to performed by a panel of content and instru-
be measured based on the result of concept ment experts. once it is determined that the
clarification. operationalization is the pro- concept is adequately indexed, a second phase
cess of moving to a variable that is isomor- of testing involves the use of the instrument
phic with the theoretical definition and is with a sample from the target population.