The Psychometric Development of WeD-QoL Measure
(Phase 4)
In a nutshell. Full psychometric report to
follow.
1. Ultimately the aim of this process is to get
a battery of items that efficiently and reliably measures QoL
in Developing Countries. It will consist of a set of easy to interpret
factors that make sense, psychologically and contextually, and
could potentially be replicated on further samples of people in
developing countries.
2. We cannot determine the precise outcome until the analyses
have been completed, but the resulting WeD-QoL measure will be
usable as a battery in its own right, the score or scores from
which will indicate level of subjective QoL, and can be used in
further analyses, as a dependent or independent variable.
3. Prior to the psychometric analyses, we do not know what the
content of this battery (or set of scales) will be. We do not
know the best number of factors (as that depends on decisions
we make with the statistical output), or what the items are which
load on those factors (and therefore form part of the battery).
4. In Phase 1 we have gone through the process of administering
a large pool of items to a large sample of the population for
whom the test is to be designed (people in developing countries).
Via Phase 2 and 3 we have included in this pool of items those
which we believe (from earlier phases of the research) to measure
some aspect of QoL. In Phase 4 we will now use the data to develop
a simple and valid measure of WeD QoL.
5. The psychometric process will determine the 'best' scales from
the pool of items. 'Best' means being the most interpretable,
reliable (internally consistent), valid (in that it can be shown
to measure what we intend it to measure), replicable (across further
samples) and simple (in terms of factor structure).
6. Scale development involves a process of item and factor analysis,
resulting in a range of several potential factor structures. These
are then assessed (via exploratory and confirmatory factor analysis)
to decide which is the 'best'. Each of the resultant factors becomes
a sub-scale, with the items that load on each factor being the
items which that subscale comprises. Then, reliability analysis
for each subscale is conducted in order to get the best internal
coherence. In this process some items may be deleted from the
ultimate measure.
7. The traditional approach would be to then re-administer the
scale to a new sample and subject it to further psychometric analyses.
Due to the high costs of fieldwork in multi-cultural research,
our planned alternative approach is to ‘virtually’
re-administer the scale on the existing databases. This is a procedure
which has been applied successfully in previous research.
8. Iterations of the same analysis process will be performed on
both the pooled 4 country data and the individual country datasets,
starting with a general solution based on the 4 country data then
a solution which builds in (as restrictions) the differences between
countries.
9. The aim is to achieve a cross-cultural scale, which focuses
on the common routes of the multiple cultures, and is valid and
reliable for each country. This will enable comparability of QoL
between the four countries.
10. A second aim is to be able to explore the uniqueness of QoL
in each country, bearing in mind the country-specific items that
were included in the item pool at Phase 3 alongside the main set
of items which were common across all countries. To do this, exploratory
then confirmatory factor analysis will also be run on each country
dataset, with reliability analyses to achieve the best solutions.
The specific country solutions will then be compared with a) the
4 countries solution and b) with the restricted (to that country)
4 countries solution mentioned in (8) above.
11. One possible outcome is that we achieve the same factor solution
for all the countries separately as for the pooled data, with
the country specific items loading on particular factors within
that. These country specific items could then add to the strength
of the measure for those countries, whereas others may be discarded.
12. Another possible outcome is that exactly the same set of items
(from the common item pool) provides the best factor solution
for all four of the countries.
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