Development and validation of the newly developed Preschool Theory of Mind Assessment (ToMA-P).

Introduction: Theory of mind (ToM) refers to the ability to understand and attribute mental states to oneself and others. A ToM measure is warranted for preschool children to assess their ToM development from a multidimensional perspective (i.e., cognitive and affective dimensions). This study aimed to develop the Preschool Theory of Mind Assessment (ToMA-P) and to evaluate its construct validity and applicability. Methods: The ToMA-P was developed based on comprehensive literature review and revised with expert panel feedback. Its psychometric properties were evaluated in 205 typically developing preschoolers with Rasch analysis for its dimensionality, item difficulties, and convergent validity. Results: The results indicated that all ToMA-P items, except for one, fit the hypothesized two-dimensional construct. The item difficulties in the cognitive and affective dimensions followed developmental sequences. The ToMA-P scores exhibited good convergent validity, as evidenced by its significant correlations with age, verbal comprehension, adaptive functions, and daily ToM performance (p < 0.05). Children's responses and behaviors also showed that the ToMA-P has good applicability. Discussion: This study provides empirical evidence that the ToMA-P measures cognitive and affective ToM following developmental sequences, and that it has potential as a clinical tool for assessing ToM in preschool children.

Theory of Mind Predicts Social Interaction in Children with Autism Spectrum Disorder: A Two-Year Follow-Up Study.

This two-year follow-up study examined the predictive relationships of theory of mind (ToM) to social interaction by reciprocal social behaviors (RSBs) and social functioning (SF) in 106 children with ASD. The results of the path analysis showed that the earlier ToM predicted children's current component RSBs (B = 3.53, SE = 1.86, p = 0.039) and the current SF (B = 1.79-1.87, SE = 0.03-0.34, p < 0.001). The aloof and passive social interaction styles predicted fewer turn-taking of RSBs (B = - 48.77 to - 111.17, p < 0.001) and fewer components of RSBs (B = - 36.30 to - 81.41, p < 0.001). This finding provides empirical evidence that ToM predicts social interaction in children with ASD.

Improving test efficiency for a grid multidimensional computerized classification test by the application of a conditional latent-trait distribution to a sequential probability ratio test.

The measurement efficiency of a multidimensional computerized adaptive testing (MCAT) can be improved by taking the correlations between the dimensions into account during the item selection and latent-trait estimation procedures (Segall, 1996; Wang & Chen, 2004). Although a multidimensional computerized classification test (MCCT), which was based on a multidimensional itemresponse model, was previously found more efficient than its unidimensional counterpart, the difference was negligible (Seitz & Frey, 2013); the researchers had adopted a sequential probability ratio test (SPRT) as the termination criterion in this MCCT study. To make a classification decision on each dimension, which is called a grid classification (Wang et al., 2019), only items that loaded on that dimension were used to calculate the likelihood ratio, which squandered the available information of the correlations between the dimensions. The current study utilizes such useful information to improve the measurement efficiency of the MCCT by applying a conditional distribution of the latent-trait estimates and then including all the administered items to calculate the likelihood ratio in the SPRT. The performance of this newly proposed method was evaluated through a series of simulation studies. The results showed that the proposed method can sizably improve the measurement efficiency of an MCCT by saving 1% to 32% of the test length in comparison with the SPRT when the two test dimensions are at least moderately correlated. The findings and further applications of this study are discussed.

Development of the Computerized Adaptive Test of Motor Development (MD-CAT) Adopting Multidimensional Rasch Analysis.

OBJECTIVE: This study aimed to develop the Computerized Adaptive Test of Motor Development (MD-CAT) in preschool children based on multidimensional Rasch analysis. DESIGN: A retrospective study with cross-sectional design. SETTING: A medical center. PARTICIPANTS: A total of 1738 children (N=1738). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: MD-CAT. RESULTS: Multidimensional Rasch analysis was used to develop the item bank of the MD-CAT. The item bank of the MD-CAT contained 74 items, with 44 and 30 items, respectively, for the subscales of gross and fine motor skills. High correlation existed between the 2 subscales (r=0.96). Three stopping rules were set for the MD-CAT: (1) the person reliability achieved 0.95 or the limited reliability increase by <0.01; (2) at least 3 items were assessed in each dimension; and (3) the number of items used for assessment reached 16. Based on the 3 stopping rules, the MD-CAT had high correlations with its total test length (r=0.87-0.98 for the 2 dimensions), indicating sufficient construct validity. The MD-CAT also had adequate diagnostic validity (area under the curve=0.72-0.93) and efficiency (an average of 3-6 items used for the assessment). CONCLUSIONS: The MD-CAT has high precision and efficiency, good construct validity, and high diagnostic validity. The results of our study indicate that the MD-CAT can be useful in clinical practice and in research as a diagnostic measure.

Development of a battery of phase-adaptive health literacy tests for stroke survivors.

OBJECTIVE: We aimed to develop a health literacy battery for three phases of stroke (HL-3S). METHODS: Three Rasch-based item banks corresponding to health care, disability prevention, and health promotion in the acute, subacute, and chronic phases of stroke, respectively, were developed by a multidisciplinary stroke team. To construct the HL-3S, a panel of clinical and Rasch experts selected items from the three Rasch-based item banks according to content representativeness and item difficulty diversity. Additionally, the validity and reliability of the HL-3S were examined using Rasch analysis. RESULTS: This study included 442 patients. Each of the three tests in the HL-3S contained 10 items with a 5-point scale of difficulty levels. The items in HL-3S demonstrated unidimensionality, local independence, and favorable Rasch reliability. CONCLUSION: The HL-3S, with 10 items in each test, had favorable construct validity and Rasch reliability. The HL-3S can be considered as a quick-to-administer and phase-adaptive test battery of health literacy for stroke survivors. PRACTICE IMPLICATIONS: Clinicians may select one of the tests in the HL-3S corresponding with the patient's stroke recovery timeline and thereby provide adaptive health education programs to increase the patient's ability to actively participate in health care, disability prevention, and health promotion, respectively.

Psychometric Properties and Efficiency of the Computerized Adaptive Testing System for Measuring Self-Care Performance in Taiwanese Children With Developmental Disabilities.

OBJECTIVE: To investigate the psychometric properties and efficiency of the computerized adaptive testing system for measuring self-care performance (CAT-SC). The psychometric properties included intrarater and interrater reliabilities, concurrent validity, minimal detectable change, minimal important difference, and responsiveness. DESIGN: Criterion standard study. SETTING: A teaching hospital. PARTICIPANTS: A convenience sample of 60 caregivers of children with developmental disabilities was recruited at the initial assessment, and 95% of the children (N=57) were followed-up at 3 and 6 months. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The CAT-SC and the Pediatric Evaluation of Disability Inventory Chinese version were used at the initial assessment. We assessed the CAT-SC and asked caregivers to rate children's changes in self-care performance with a separate question rated on a 15-point Likert-type scale at the 3- and 6-month follow-ups. RESULTS: The CAT-SC had excellent intrarater and interrater reliabilities (intraclass coefficient=0.99 and 0.92, respectively), high concurrent validity with the Pediatric Evaluation of Disability Inventory (r=0.91-0.92), and trivial to small responsiveness at 3- and 6-month follow-ups (effect size=0.02 and 0.12, standardized response mean=0.08 and 0.33). The minimal detectable change of intrarater reliabilities and the minimal important difference at the first follow-up were 0.22 and 0.17 logits, respectively. The administration time of the CAT-SC was about 5 minutes. CONCLUSIONS: The results of our study validated the sound psychometric properties and good efficiency of the CAT-SC. Moreover, the values of the minimal detectable change and minimal smallest change can be used as a reference for clinicians and caregivers to interpret children's progress.

Identifying the Cognitive Correlates of Reciprocity in Children with Autism Spectrum Disorder.

This study examined the cognitive correlates of reciprocity in children with autism spectrum disorder (ASD). A total of 59 children with ASD were assessed with the Interactive Drawing Task, Theory of Mind Task Battery, Children's Card Change Sort Task, and Children's Gambling Task respectively for their reciprocity, theory of mind, cool executive function (EF), and hot EF. The correlational findings revealed that cool EF (r = .482 and - .501, p < .01) and hot EF (r = .396, p < .05) were significantly correlated with children's total reciprocity. The regression models also showed that cool and hot EF abilities were significant predictors. Conclusively, cool and hot EF abilities are the correlates of reciprocity rather than of ToM in children with ASD.

Rasch Analysis of the 9-Item Shared Decision Making Questionnaire in Women With Breast Cancer.

BACKGROUND: Shared decision making (SDM) is a best practice to help patients make optimal decisions by a process of healthcare, especially for women diagnosed with breast cancer and having heavy burden in long-term treatments. To promote successful SDM, it is crucial to assess the level of perceived involvement in SDM in women with breast cancer. OBJECTIVE: The aims of this study were to apply Rasch analysis to examine the construct validity and person reliability of the 9-item Shared Decision Making Questionnaire (SDM-Q-9) in women with breast cancer. METHODS: The construct validity of SDM-Q-9 was confirmed when the items fit the Rasch model's assumptions of unidimensionality: (1) infit and outfit mean square ranged from 0.6 to 1.4; (2) the unexplained variance of the first dimension of the principal component analysis was less than 20%. Person reliability was calculated. RESULTS: A total of 212 participants were recruited in this study. Item 1 did not fit the model's assumptions and was deleted. The unidimensionality of the remaining 8 items (SDM-Q-8) was supported with good item fit (infit and outfit mean square ranging from 0.6 to 1.3) and very low unexplained variance of the first dimension (5.3%) of the principal component analysis. The person reliability of the SDM-Q-8 was 0.90. CONCLUSIONS: The SDM-Q-8 was unidimensional and had good person reliability in women with breast cancer. IMPLICATIONS FOR PRACTICE: The SDM-Q-8 has shown its potential for assessing the level of perceived involvement in SDM in women with breast cancer for both research and clinical purposes.

Prediction Of Playfulness By Pretend Play, Severity Of Autism Behaviors, And Verbal Comprehension In Children With Autism Spectrum Disorder.

BACKGROUND: Children with autism spectrum disorder (ASD) often exhibit deficits in pretend play and have less playfulness. The purpose of this study was to evaluate the relationship between pretend play and playfulness in children with autism spectrum disorder, while controlling for severity of autism behaviors, verbal comprehension, and age. METHODS: A sample of 72 children with ASD aged between 3 and 12 years were assessed with the Child-Initiated Pretend Play Assessment, Test of Playfulness, and Childhood Autism Rating Scale, respectively, for their pretend play, playfulness, and severity of autism behaviors. Correlation and multiple regression analyses were conducted. RESULTS: The results of Pearson correlation coefficients revealed that the pretend play variables had mild to moderate associations with the playfulness variables (r = -0.25 to 0.68). The multiple regression analyses showed that, overall, the internal locus of control was the significant predictor of the pretend play variables (accounting for 5-47% of the variance, p < 0.001). The six pretend play variables were all important predictors of all playfulness variables (explaining 41-76% of the variance, p < 0.001-0.047). Particularly, the elaborate pretend play action was a significant predictor of all four playfulness variables. Our findings indicated that the more children with ASD engaged in pretend play, the more they experienced playfulness. CONCLUSION: Clinicians could help children with ASD improve their feeling of being in charge of their play in order to develop better performance in pretend play. Assisting children with ASD to engage in pretend play is important to promote their internal experience of playfulness.

Improving the Assessment of Differential Item Functioning in Large-Scale Programs With Dual-Scale Purification of Rasch Models: The PISA Example.

By design, large-scale educational testing programs often have a large proportion of missing data. Since the effect of missing data on differential item functioning (DIF) assessment has been investigated in recent years and it has been found that Type I error rates tend to be inflated, it is of great importance to adapt existing DIF assessment methods to the inflation. The DIF-free-then-DIF (DFTD) strategy, which originally involved one single-scale purification procedure to identify DIF-free items, has been extended to involve another scale purification procedure for the DIF assessment in this study, and this new method is called the dual-scale purification (DSP) procedure. The performance of the DSP procedure in assessing DIF in large-scale programs, such as Program for International Student Assessment (PISA), was compared with the DFTD strategy through a series of simulation studies. Results showed the superiority of the DSP procedure over the DFTD strategy when tests consisted of many DIF items and when data were missing by design as in large-scale programs. Moreover, an empirical study of the PISA 2009 Taiwan sample was provided to show the implications of the DSP procedure. The applications as well as further studies of DSP procedure are also discussed.

Item-saving assessment of self-care performance in children with developmental disabilities: A prospective caregiver-report computerized adaptive test.

OBJECTIVE: The purpose of this study was to construct a computerized adaptive test (CAT) for measuring self-care performance (the CAT-SC) in children with developmental disabilities (DD) aged from 6 months to 12 years in a content-inclusive, precise, and efficient fashion. METHODS: The study was divided into 3 phases: (1) item bank development, (2) item testing, and (3) a simulation study to determine the stopping rules for the administration of the CAT-SC. A total of 215 caregivers of children with DD were interviewed with the 73-item CAT-SC item bank. An item response theory model was adopted for examining the construct validity to estimate item parameters after investigation of the unidimensionality, equality of slope parameters, item fitness, and differential item functioning (DIF). In the last phase, the reliability and concurrent validity of the CAT-SC were evaluated. RESULTS: The final CAT-SC item bank contained 56 items. The stopping rules suggested were (a) reliability coefficient greater than 0.9 or (b) 14 items administered. The results of simulation also showed that 85% of the estimated self-care performance scores would reach a reliability higher than 0.9 with a mean test length of 8.5 items, and the mean reliability for the rest was 0.86. Administering the CAT-SC could reduce the number of items administered by 75% to 84%. In addition, self-care performances estimated by the CAT-SC and the full item bank were very similar to each other (Pearson r = 0.98). CONCLUSION: The newly developed CAT-SC can efficiently measure self-care performance in children with DD whose performances are comparable to those of TD children aged from 6 months to 12 years as precisely as the whole item bank. The item bank of the CAT-SC has good reliability and a unidimensional self-care construct, and the CAT can estimate self-care performance with less than 25% of the items in the item bank. Therefore, the CAT-SC could be useful for measuring self-care performance in children with DD in clinical and research settings.

Evaluating the European Health Literacy Survey Questionnaire in Patients with Stroke: A Latent Trait Analysis Using Rasch Modeling.

BACKGROUND: The effective self-management and treatment of long-term disability after stroke depends greatly on the health literacy of patients. The European Health Literacy Survey Questionnaire (HLS-EU-Q) is a comprehensive and theory-based measure that captures multiple self-perceived competencies of health literacy and covers a diverse range of health contexts. However, there is no psychometric evidence on the HLS-EU-Q in the stroke population. OBJECTIVE: The aim of this study was to examine the validity of the HLS-EU-Q in patients with stroke using Rasch analysis. METHODS: We compared the model deviance among the one-domain, three-domain, four-domain, and 12-domain structures using likelihood ratio tests to determine the dimensionality of the HLS-EU-Q. Thereafter, we examined the unidimensionality of each domain, local independence, item fit, response categories, and differential item functioning (DIF) for the best fitting structure. RESULTS: A total of 311 patients with stroke participated in this study. Rasch analysis revealed that the 12-domain HLS-EU-Q demonstrated the best data-model fit. The original 4-point scales showed disordering, which can be corrected by rescaling them as 3-point scales with the two middle categories collapsed. All 47 items in the rescaled HLS-EU-Q fit the 12-domain Rasch model, demonstrated local independence, assessed the 12 unidimensional domains respectively, and had invariant difficulties between different age or education groups of the patients with stroke. CONCLUSION: We recommend using the 12-domain scores of the rescaled HLS-EU-Q to comprehensively and accurately capture the competencies to access, understand, appraise, and apply health information within the three health contexts of healthcare, disease prevention, and health promotion for patients with stroke.

Validation of the Integrated Model of Health Literacy in Patients With Breast Cancer.

BACKGROUND: Health literacy (HL) enables patients with breast cancer to actively participate in health decisions and promote positive health outcomes. The Integrated Model of Health Literacy (IMHL), defined as the personal, situational, and societal/environmental factors that predict the level of HL that can influence health outcomes, incorporates the concepts, determinants, and consequences of HL. OBJECTIVE: The aim of this study was to examine the mechanisms and completeness of the IMHL in patients with breast cancer. METHODS: Five hundred eleven Taiwanese patients were prospectively recruited. We conducted structural equation modeling to confirm and modify the predictive pathways linking the HL-related factors in the IMHL. RESULTS: Results on a total of 511 breast cancer patients showed good model-data fit. An alternative model revealed better fit with 2 pathways added from cancer stage to self-rated health and from cancer duration to shared decision making. Both the original model and alternative model modification revealed that only personal determinants (age, education, cancer stage, and duration) and not situational determinants (marital status) or social/environmental determinants (residence and occupation) could significantly predict the 3 domains of HL. Theorized consequences of HL were significantly influenced by HL in both models. CONCLUSIONS: Our results partially support the relationships proposed in the IMHL for patients with breast cancer as only personal determinants significantly predicted HL. IMPLICATIONS FOR PRACTICE: Understanding the predictive pathways of the integrated HL model could help clinicians to tailor HL interventions using a patient's personal determinants to facilitate participation in decision making and promote health for breast cancer patients.

Theory of Mind Deficit is Associated with Pretend Play Performance, but not Playfulness, in Children with Autism Spectrum Disorder.

OBJECTIVE/BACKGROUND: This study aimed to examine the relationships of theory of mind (ToM) to both pretend play and playfulness in children with autism spectrum disorder (ASD). METHODS: Twenty children with ASD aged between 3 years and 7.11 years were assessed with the ToM test, and then placed in a free play condition and a pretend play condition to assess pretend play and playfulness with the Child-Initiated Pretend Play Assessment and Test of Playfulness, respectively. In addition, the children's symptom severities of ASD and verbal abilities were also assessed with the Childhood Autism Rating Scale (CARS) and Receptive and Expressive Vocabulary Test-second edition, respectively. RESULTS: The results of the regression analysis confirmed that ToM significantly predicted pretend play variables, namely, Number of Object Substitutions (R2 = .158, p = .002) and Number of Imitated Actions (R2 = .175, p = .001), but not playfulness. The CARS score was a significant predictor of the Percentage of Elaborate Pretend Play Actions of pretend play (R2 = .075, p = .034), as well as the internal control (R2 = .125, p = .006) and framing (R2 = .071, p = .039) variables of playfulness. CONCLUSION: The findings support the idea that children with ASD who have better ToM might be able to develop better pretend play, but not better playfulness, which might be more strongly related to their autistic severity.

Validation of the short-form Health Literacy Scale in patients with stroke.

OBJECTIVE: We aimed to validate a Mandarin version of the short-form Health Literacy Scale (SHEAL) in patients with stroke. METHODS: Each patient with stroke was interviewed with the SHEAL. The Public Stroke Knowledge Quiz (PSKQ) was administered as a criterion for examining the convergent validity of the SHEAL. The discriminative validity of the SHEAL was determined with age and education level as independent grouping variables. RESULTS: A total of 87 patients with stroke volunteered to participate in this prospective study. The SHEAL demonstrated sufficient internal consistency reliability (alpha=0.82) and high correlation with the PSKQ (r=0.62). The SHEAL scores between different age groups and education level groups were significantly different. The SHEAL, however, showed a notable ceiling effect (24.1% of the participants), indicating that the SHEAL cannot differentiate level of health literacy between individuals with high health literacy. CONCLUSION: The internal consistency reliability, convergent validity, and discriminative validity of the SHEAL were adequate. However, the internal consistency reliability and ceiling effect of the SHEAL need to be improved. PRACTICE IMPLICATIONS: The SHEAL has shown its potential for assessing the health literacy of patients with stroke for research purposes. For clinical usage, however, the SHEAL should be used with caution.

A prospective study of the responsiveness of the original and the short form Berg Balance Scale in people with stroke.

OBJECTIVE: The study aim was to examine the responsiveness of the Berg Balance Scale (BBS) and that of its short form (SFBBS) at both the individual person level and the group level. DESIGN: A repeated-measurements design. SETTING: Hospital and home setting. PARTICIPANTS: Patients with stroke. RESULTS: Totals of 226, 202, and 168 patients with stroke were assessed with the BBS at 14, 30, and 90 days after stroke, respectively. The SFBBS data were extracted from the patients' responses on the BBS. At the group level, the BBS and the SFBBS had sufficient and similar responsiveness. For the Rasch scores, the effect sizes of the three change scores for the BBS and the SFBBS, respectively, had similar ranges between 0.38 and 0.88 and between 0.39 and 0.85, respectively. The standardized response means of the three change scores for the BBS and the SFBBS ranged from 0.74 to 1.33 and from 0.72 to 1.13, respectively. At the individual person level, the BBS detected significant balance improvement in about twice as many patients as the SFBBS detected. CONCLUSION: The responsiveness of the BBS at the individual person level was better than that of the SFBBS in patients with stroke. The BBS is recommended as an outcome measure to better detect changes in individual patients.

Is the long form of the Fugl-Meyer motor scale more responsive than the short form in patients with stroke?

OBJECTIVE: To compare the responsiveness of the Rasch-calibrated 37-item Fugl-Meyer motor Scale with that of the 12-item Fugl-Meyer motor scale at both an individual and a group level. DESIGN: Repeated-measurements design. SETTING: Medical center. PARTICIPANTS: Patients (N=301) 14 days after stroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: 50-item Fugl-Meyer motor scale, 37-item Fugl-Meyer motor scale, and 12-item Fugl-Meyer motor scale. RESULTS: The patients were assessed with the original 50-item Fugl-Meyer motor scale 4 times, at 14, 30, 90, and 180 days after stroke onset. The patients' responses were used for estimating the Rasch scores of the 37-item Fugl-Meyer motor scale and 12-item Fugl-Meyer motor scale. The effect size, standardized response mean, and paired t test were used to compare the group-based responsiveness of the 3 forms (50-item Fugl-Meyer motor scale, 37-item Fugl-Meyer motor scale, 12-item Fugl-Meyer motor scale). Individual-level responsiveness was compared based on the significance of change between the 37-item Fugl-Meyer motor scale and 12-item Fugl-Meyer motor scale. Because up to 13 items of the 50-item Fugl-Meyer motor scale did not meet the Rasch model's assumptions, the significance of change of the 50-item Fugl-Meyer motor scale was not calculated. At the group level, the FM-37 and FM-12 Fugl-Meyer motor scale had sufficient and similar responsiveness. At the individual level, the FM-37 Fugl-Meyer motor scale detected more patients with significant improvement than the FM-12 Fugl-Meyer motor scale. The SC values and category distribution of the FM-37 Fugl-Meyer motor scale were significantly better than those of the FM-12 Fugl-Meyer motor scale (P<.001). CONCLUSIONS: Although the group-level responsiveness of the 12-item Fugl-Meyer motor scale was sufficient and very similar to that of the 37-item Fugl-Meyer motor scale, the 37-item Fugl-Meyer motor scale had better individual-level responsiveness. The 37-item Fugl-Meyer motor scale is suggested as an outcome measure for both clinicians and researchers.

Development of a computerized adaptive test for assessing balance function in patients with stroke.

BACKGROUND: An efficient and precise measure of balance is needed to improve administration efficiency and to reduce the assessment burden for patients. OBJECTIVE: The purpose of this study was to develop a computerized adaptive testing (CAT) system for assessing balance function in an efficient, reliable, and valid fashion in patients with stroke. DESIGN: Two cross-sectional prospective studies were conducted. SETTING: This study was conducted in the departments of physical medicine and rehabilitation in 6 hospitals. PATIENTS: The participants were inpatients and outpatients who were receiving rehabilitation. MEASUREMENTS: A balance item pool (41 items) was developed on the basis of predefined balance concepts, expert opinions, and field testing. The items were administered by 5 raters to 764 patients. An item response theory model was fit to the data, and the item parameters were estimated. A simulation study was used to determine the performance (eg, reliability, efficiency) of the Balance CAT. The Balance CAT and the Berg Balance Scale (BBS) then were tested on another independent sample of 56 patients to determine the concurrent validity and time needed for administration. RESULTS: Seven items did not meet the model's expectations and were excluded from further analysis. The remaining 34 items formed the item bank of the Balance CAT. Two stopping rules (ie, reliability coefficient > 0.9 or < or = 6 items) were set for the CAT. The simulation study showed that the patients' balance scores estimated by the CAT had an average reliability value of .94. The scores obtained from the CAT were closely associated with those of the full item set (Pearson r=.98). The scores of the Balance CAT were highly correlated with those of the BBS (Pearson r=.88). The average time needed to administer the Balance CAT (83 seconds) was only 18% of that of the BBS. LIMITATIONS: The convenience sampling of both samples may limit the generalization of the results. Further psychometric investigation of the Balance CAT is needed. CONCLUSION: The results provide strong evidence that the Balance CAT is efficient and has reliability and validity for patients with stroke.

Using SAS PROC NLMIXED to fit item response theory models.

Researchers routinely construct tests or questionnaires containing a set of items that measure personality traits, cognitive abilities, political attitudes, and so forth. Typically, responses to these items are scored in discrete categories, such as points on a Likert scale or a choice out of several mutually exclusive alternatives. Item response theory (IRT) explains observed responses to items on a test (questionnaire) by a person's unobserved trait, ability, or attitude. Although applications of IRT modeling have increased considerably because of its utility in developing and assessing measuring instruments, IRT modeling has not been fully integrated into the curriculum of colleges and universities, mainly because existing general purpose statistical packages do not provide built-in routines with which to perform IRT modeling. Recent advances in statistical theory and the incorporation of those advances into general purpose statistical software such as the Statistical Analysis System (SAS) allow researchers to analyze measurement data by using a class of models known as generalized linear mixed effects models (McCulloch & Searle, 2001), which include IRT models as special cases. The purpose of this article is to demonstrate the generality and flexibility of using SAS to estimate IRT model parameters. With real data examples, we illustrate the implementations of a variety of IRT models for dichotomous, polytomous, and nominal responses. Since SAS is widely available in educational institutions, it is hoped that this article will contribute to the spread of IRT modeling in quantitative courses.