心理計量文獻閱讀問題-單向度

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