BACKGROUND For the Low Vision Quality Of Life questionnaire (LVQOL) it is unknown whether the psychometric properties are satisfactory when an item response theory (IRT) perspective is considered. This study evaluates some essential psychometric properties of the LVQOL questionnaire in an IRT model, and investigates differential item functioning (DIF). METHODS Cross-sectional data were used f...

To satisfy the requirement of high performance signal processing technique, it is necessary to use the direct sampling of intermediate frequency signal to obtain quadrature signals. Digital intermediate frequency (DIF) system is widely used in radar and communication system. This paper briefly introduces the principle of test system based on DIF. We design this DIF test system to test the perfo...

The Roussos-Stout (1996) multidimensionality-based DIF analysis framework emphasizes a substantively-informed selection of items for both the matching and studied subtest based on the dimensions suspected of underlying the test data. By contrast, standard DIF practice encourages an exploratory search for matching subtest items based on purely statistical criteria, such as a failure to display D...

Differential item functioning (DIF) indicates the violation of the invariance assumption for instance in models based on item response theory (IRT). For item-wise DIF analysis using IRT, a common metric for the item parameters of the groups that are to be compared (e.g. for the reference and the focal group) is necessary. In the Rasch model, therefore, the same linear restriction is imposed in ...

A previous report described an intracellular factor (differentiation-inducing factor I, or DIF-I) that seems to play a role in erythroid differentiation in mouse erythroleukemia (MEL) cells. We have detected another erythroid-inducing factor in cell-free extracts from dimethyl sulfoxide- or hexamethylenebis(acetamide)-treated MEL cells, which acts synergistically with DIF-I. The partially purif...

Background The aim of this study was to test the General Oral Health Assessment Index Questionnaire (GOHAI) items for differential item functioning (DIF) according to demographic characteristics (gender, age) and mental health status (schizophrenic disorders versus general population) using Rasch analysis. Methods This is a cross-sectional study using aggregated baseline data from a validatio...

Survival of all animals depends on effective protection against infection. In Drosophila, opportunistic infection kills larvae if they lack the Rel/NF-kappaB proteins Dorsal and Dif. We have used tissue-specific expression of Dif and Dorsal to reveal that these Rel proteins act in three different tissues to defend larvae from infection. Dif and Dorsal act in circulating blood cells, where they ...

Expression of the gene encoding the antifungal peptide Drosomycin in Drosophila adults is controlled by the Toll signaling pathway. The Rel proteins Dorsal and DIF (Dorsal-related immunity factor) are possible candidates for the transactivating protein in the Toll pathway that directly regulates the drosomycin gene. We have examined the requirement of Dorsal and DIF for drosomycin expression in...

Over the past years the percentage of female entrepreneurs has increased, yet it is still far below of that for males. Although various attempts have been made to explain differences in mens' and women's entrepreneurial attitudes and intentions, the extent to which those differences are due to self-report biases has not been yet considered. The present study utilized Differential Item Functioni...

BACKGROUND Little is known about cross-language measurement equivalence of the job content questionnaire (JCQ) PURPOSE: The purposes of this study were to assess the extent of cross-language differential item functioning (DIF) of the 27 JCQ items in six languages (French, Dutch, Belgian-French, Belgian-Dutch (Flemish), Italian, and Swedish) from six European research centers and to test whether...