The reviewers of our MS asked the following questions need to be answered:
Considering the questionnaire has been not previously used in this population and that it is the main outcome measure used in this study, it should be validated. This could be done with some form of item response theory using this data set. i.e. Rasch analysis.  Rasch analysis will test the assumptions (a) the common assignment of numbers to responses represents fundamental measurement and therefore allows for arithmetic operations such as addition and subtraction, and (b) all items in a questionnaire are of the same difficulty.  

a怎么搞啊,证明1-5个等级的同意程度可以当作数来运算
b为什么要求相同的难度系数啊,rasch analysis不是只用来证明所有题目是反映一个trait的就可以了么,题目不同难度没有关系吧.

现在的情况是我做了个pathway的图看,发现8个item的infit都很大,不满足-2---2的chisquare要求 说明测的不是一个trait??
怎么办啊,尤其是a应该怎么说明啊,一般好像都是默认的加起来算score用了,没找到什么资料讲这里面的道理的

大家帮忙啊,我是新手