依據 difficulty parameter, why is playing chess/cards more difficult than gainful work? It seems to me that the result of this analysis suffered from a common problem with Rasch analysis, namely that frequency of performance is confused with difficulty of performance. Please see Whiteneck G, Dijkers MP. Difficult to measure constructs: conceptual and methodological issues concerning participation and environmental factors. Arch Phys Med Rehabil. 2009 Nov;90(11 Suppl):S22-35 on the limitations of Rasch analysis in the context of participation (or instrumental ADL).
如下圖：依據 Rasch analysis 分析結果， Reading 的難度 > Work > Preparing meal > Heavy housework 這似乎違背邏輯/經驗！！
請以中文解釋之，含其臨床意義。
9/26日之前提出。
可單獨或團隊提出。
image source: https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcR-MLm6Mt_SX9T30vZrnUDcpR7dRotc6vbVBMn-qVW3g9pflovl
Comment: The results of table 2 are intriguing. Why is playing
chess/cards more difficult than gainful work? The same for art activities? It
seems to me that the result of this analysis suffered from a common problem
with Rasch analysis, namely that frequency of performance is confused with
difficulty of performance. Please see Whiteneck G, Dijkers MP. Difficult
to measure constructs: conceptual and methodological issues concerning
participation and environmental factors. Arch Phys Med Rehabil. 2009 Nov;90(11
Suppl):S22-35 on the limitations of Rasch analysis in the context of
participation (or instrumental ADL).
* Response: It was our mistake to state that “The items are largely listed in
increasing level of difficulty.” We have deleted the statement. The items’
level of difficulty cannot be simply determined by their order (or parameter of
step difficulty) for two reasons. The first is that there are various steps of
difficulty (various numbers of item response categories). The second is that
the discrimination parameter also affects the hierarchy of item difficulty.
That is, some items might be more difficult at certain level of function, but
they might be easier at another level of function. This is a potential drawback
of the 2-parameter model. We have addressed this issue as follows:
“We used the GPCM (a type of 2-paramter IRT
model, including discrimination and difficulty parameters)34
to fit the patients’ responses and estimate the item parameters for the ADL
item bank. The GPCM is a flexible model from the parametric, unidimensional,
polytomous-response IRT models. Because GPCM allows discrimination to vary from
item to item, it generally fits response data better than a 1-parameter model
(e.g., Rasch model).35
However, using a 2-parameter IRT model may have made the results difficult to
interpret. For example, an item’s level of difficulty cannot be simply
determined by its “difficulty” parameter (i.e., step threshold) because the
discrimination parameter (i.e., slope) also affects the hierarchy of item
difficulty. That is, some items might be more difficult at certain levels of
function, but they might be easier at other levels of function. This is a
potential drawback of the 2-parameter model. Nevertheless, the 2-parameter IRT
model is suggested due to its flexibility and is adopted by several
health-related CATs.12, 15, 36”
Furthermore, “Even if the
discrimination parameter is fixed, explanations of an item’s value of
“difficulty” parameter have to be cautious. For example, our results showed
that the value (3.54) of difficulty parameter of “volunteer work” was
unexpectedly higher than that (2.53) of “gainful work” (Table 2). The value of
difficulty parameter is commonly interpreted as the “level of difficulty or
challenge” of a task. The difficulty parameter of an item is influenced by how
often patients perform the task.22 Appendix 1 shows that only a small proportion
of the patients had been working (gainful work (7.1%) and volunteer work
(3.1%)). However, that frequency might not necessarily indicate the level of
difficulty of a task. Particularly, the patients tested were all outpatients,
who were unlikely to seek and do volunteer work. On the other hand, gainful
employment is often an obligation or responsibility. Thus, the value of
difficulty parameter is not equal to the level of challenge of an ADL task.37 In addition, as aforementioned, we used a
2-parameter model, not the 1-parameter IRT model. Due to these issues, our data
are not sufficient to determine whether an item with a low value of difficulty
(e.g., doing gainful work) is less challenging than an item with a high value
of difficulty (e.g., doing volunteer work).”
Your further comments are appreciated!
