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1) Although the author put the P=0 as the bottom category of Severity part, We still non-creative. We should try to use multidimentional or higher order IRT to trait this P-S format. I mean we can let P part as one latent trait and S part as another.
2) It seems some typing mistake in Table 2c. I think the author lose to list p=2,s=0 and p=2,s=1 in Table 2c.
3) I didn't study the characteristic of NRM which is strange to me. Firstly, the constrain of sum(step difficulties by each category within item)=0 means that all the average of step difficulty within item equals to zero. secondly, I don't understand why the increasing trend of slop parameter in NRM can represent the ordinality of the response categories. Does it means the larger category with higher slop parameter is reasonable?
4) I don't know the JCA which is a kind of exploratory method has been used to test the unidimensional assumption. Is it too rarely to use?
5) The correlation of NRM or GPCM with total score in Table 4 listing here couldn't lead a meaningful interpretation. The author just used table 4 to illustrate these three model still are different scoring model although the correlation among them is very high.