Q.
1. Guttman scales相加之overall
scores是否有意義
2. Rasch是否不適合驗證單向度?欲轉成interval scale才用rasch?若只為確認單向度驗證Mokken?
Guttman scales是更簡易之指標?
3. 何謂”IRFs of the scale do not intersect?"
4. Mokken指標The scalability coefficient H : a global indicator of the degree to
which patients can be accurately ordered on the
upper extremity function by means of their sum scores à此sum scores 只能做比較用，而不看能力差異之大小?
5. 何謂Intermodel agreement?
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Points:
Guttman scale
由單向或具有同一性質的項目所組成，項目由弱到強連續性排序
Standard:(to be a valid cumulative and
unidimensional Guttaman model)
Coefficient of
Reproducibility(CR): how well the observed
responses corresponded to the responses that would have been predicted if the
items were perfectly ordered. (CR>.90)
Coefficient of Scalability(CS): the proportion of responses which
can be correctly predicted from the total score (CS>.60)
Mokken analysis
1.
an non-parametric item response
theory model
2.
examine accuracy of ordering
between person’s raw sum scores
3.
need sample size>200
4.
standard: MH modal:The scalability
coefficient H>0.5
DM modal: adequate: largest Crit value
per item <40
violated: both Crit values for
an item>80
Rasch analysis
1.
parametric item response theory
model
2.
examine whether sum scores of a
measure can be transformed into interval scores.
(interval
property can quantify change and do arithmetic operations)
3.
Limitation: exclude items whose
scores cannot be transformed into an interval scale, but which do fit the
Mokken model’s expectations
