在经典测试理论框架中重新定义项目难度

Redefining Item Hardness in the Framework of CTT

在分析经典测试理论中项目难度的易度指数定义P、易度指数补定义q以及△定义对于成绩测试的不合适性和项目反应理论中项目难度与受考能力本质一致性的基础上，提出了经典理论框架中项目难度的两种新定义：固定基准参照点定义和任意基准参照点定义，解决了经典测试理论中测试成绩依赖于特定试卷这一致命缺陷的根源；还提出了项目难度的样本独立性定义，使项目参数的计算不依赖于不受考样本．

In this paper,an analysis is made of the inappropriateness for attainment tests of item facility index P, item difficuhy q,which is the complement of item facility index,and A difficulty index of classical test theory (CTT),pointing out that item difficulty and test - taker' s ability are of the same measure in item response theory.On the basis of this,the author redefined item difficulty (termed item hardness) in CTT terms:specific fundamental refer- ence point definition,and arbitrary fundamental reference point definition,The author also proposed a sample free deft- nition for item hardness,namely,making sample free calculation of item hardness possible in CTT.With the definitions proposed,test-dependent true score,the fatal liability of CTT has been uprooted,paving the road for test free mea- surement and item level test equating within the framework of CTT.The scale defined in the paper is a ratio scale.