Many scales contain both positively and negatively worded items. Reverse recoding of negatively worded items might not be enough for them to function as positively worded items do. In this study, we commented on the drawbacks of existing approaches to wording effect in mixed-format scales and used bi-factor item response theory (IRT) models to test the assumption of reverse coding and evaluate the magnitude of the wording effect. The parameters of the bi-factor IRT models can be estimated with existing computer programs. Two empirical examples from the Program for International Student Assessment and the Trends in International Mathematics and Science Study were given to demonstrate the advantages of the bi-factor approach over traditional ones. It was found that the wording effect in these two data sets was substantial and that ignoring the wording effect resulted in overestimated test reliability and biased person measures.

Inattentive responses can threaten measurement quality, yet they are common in rating- or Likert-scale data. In this study, we proposed a new mixture item response theory model to distinguish inattentive responses from normal responses so that test validity can be ascertained. Simulation studies demonstrated that the parameters of the new model were recovered fairly well using the Bayesian methods implemented in the freeware WinBUGS, and fitting the new model to data that lacked inattentive responses did not result in severely biased parameter estimates. In contrast, ignoring inattentive responses by fitting standard item response theory models to data containing inattentive responses yielded seriously biased parameter estimates and a failure to distinguish inattentive participants from normal participants; the person-fit statistic l_z was also unsatisfactory in identifying inattentive responses. Two empirical examples demonstrate the applications of the new model.

Background: The construct validity and reliability of the short form of the Wolf Motor Function Test (S-WMFT) in people with subacute stroke and chronic stroke (S-WMFT subacute stroke and chronic stroke versions) have not been investigated.Objective: The purpose of this study was to investigate the dimensionality, item difficulty hierarchy, differential item functioning (DIF), and reliability of the S-WMFT subacute stroke and chronic stroke versions in people with mild to moderate upper-extremity (UE) dysfunction.Design: This was a secondary study in which data collected from randomized controlled trials were used.Methods: Data were collected at baseline from 97 people with chronic stroke (>12 months after stroke) and 75 people with subacute stroke (3–9 months after stroke) at 3 medical centers in Taiwan. Test structure, hierarchical properties, DIF, and reliability were assessed with Rasch analysis.Results: The test structure for both versions was unidimensional. No DIF relevant to sex, age, or stroke location (hemispheric laterality) was detected. The tasks of moving a hand to a box and moving a hand to a table in the S-WMFT for subacute stroke showed a significantly high correlation. The reliability coefficients for both versions were approximately .90.Limitations: The findings were limited to people with stroke and mild to moderate impairment of UE function.Conclusions: The S-WMFT subacute stroke and chronic stroke versions are useful tools for assessing UE function in different subgroups of people with stroke and show evidence of construct validity and reliability. A high correlation between the tasks of moving a hand to a box and moving a hand to a table in the S-WMFT for subacute stroke suggests that the removal of 1 of these 2 items is warranted.