Rasch measurement in the Assessment of Growth Hormone Deficiency in adult patients

The Assessment of Growth Hormone Deficiency in Adults (AGHDA) questionnaire was previously designed, translated and validated in several European countries to evaluate the impact of the disease on Quality of Life. This study aimed to test the metric properties of the Spanish version by means of Rasch analysis. A sample of 356 consecutive adult patients with untreated GHD was included in the study. Patients responded to the questionnaire at baseline and 12 months apart. Answers were analyzed following the dichotomous logistic response model. Parameter estimates, model-data fit and separation statistics were computed. The invariance of the item parameters across time was tested in the follow-up. Rasch results were additionally employed to ascertain score changes through the calculation of the Reliable Change Index (RCI). Items varied in severity from 8.3 -16.8 units (SE= 0.4-0.5) and fit to define a unidimensional variable. The item separation index (SI)(5.2) indicates a good and reliable (0.9) separation of items along the variable that they define. Moreover, results showed the AGHDA conforms to the model expectation of item parameter invariance between administrations. The substantial (2.3) and reliable (0.8) person SI also suggests the sample was well targeted by the questionnaire. According to the RCI, 84% of the patients did not show a significant transition in their measures. Results denote the items of the AGHDA succeeded in defining a scale characterized by the interval-level of its measures, suggesting the questionnaire could be a useful complement of the clinical evaluation of GHD patients at both group and individual level.     

The assessment of diabetes knowledge and self-efficacy in a diverse population using Rasch measurement

The purpose of this research was to develop survey instruments to evaluate diabetes knowledge and self-efficacy in a diverse population, and investigate the psychometric properties of data obtained with these instruments using Rasch measurement. Two-hundred and fifty-five urban-dwelling participants with diabetes were recruited to complete surveys through independent interviews. To evaluate the association of health literacy on metabolic control, formal literacy and hemoglobin A1c fingerstick testing were performed. Rasch analysis of the data yielded item and person calibrations for self-efficacy and knowledge, with variable maps created to provide both norm and criterion-referenced interpretations. Knowledge scale person separation reliability was 0.50 and item separation reliability was 0.98; while self-efficacy scale person separation reliability was 0.72 with item separation reliability of 0.92. Statistically significant partial correlations were observed between knowledge and health literacy (r = 0.41, p<.001), and self-efficacy and hemoglobin A1c (r = -0.33, p<.001). However, there was no correlation between diabetes knowledge and hemoglobin A1c (r = 0.035, p = 0.29), or health literacy and A1c (r = 0.022, p = 0.36). Diabetes knowledge varied, with non-English speaking individuals having lower measures than English speakers (t(252) = -4.86, p<.001). Non-English speaking individuals also had lower self-efficacy measures than English speakers (t(251) = -2.68, p = .008). Current knowledge deficits and perceptions of self-management may be estimated visually through variable mapping, which may help in individualizing informational needs for people with diabetes.     

Rasch modeling and the measurement of social participation

Social participation is the main outcome of physical rehabilitation programs. The aim of this study is to improve the measurement of social participation, using an instrument called the Assessment of Life Habits Scale and the Rasch model. The interval level measurement, the dimensionality and the generalizability of the item hierarchy were verified. The data from a large sample of people with spinal cord injury was analyzed and specific results were compared with expert opinions. The main properties of the instrument were satisfactory and the agreement with expert opinion was high. Principal component analysis showed multidimensionality. The item difficulty hierarchy obtained with spinal cord injury experts was different from the one obtained with traumatic brain injury experts, indicating a different difficulty level of items in relation to each population characteristics. We conclude that the instrument is appropriate for the measurement of social participation and suggest ways to improve the instrument.     

Metric development and score reporting in Rasch measurement

This article: 1) describes problems in score reporting with the True-Score Model, 2) presents a definition of the Rasch measurement unit, the logit, 3) reviews various transformations of the logit metric, and 4) provides examples of score reporting procedures. Two data sets are used. The first contains dichotomous data drawn from responses to a multiple-response statistics examination taken by Ph.D. students; the second contains polychotomous data from a self-efficacy assessment given to war veterans suffering from Post Traumatic Stress Disorder.     

Analysis of letter name knowledge using Rasch measurement

Letter name knowledge (LNK) is a key predictor of later reading ability and has been emphasized strongly in recent educational policy. Studies of LNK have implicitly treated it as a unidimensional construct with all letters equally relevant to its measurement. However, some empirical research suggests that contextual factors can affect the measurement of LNK. In this study, we analyze responses from 909 children on measures of LNK using the Rasch model and its extensions, and consider two contextual factors: the format of assessment and the own-name advantage, which states that children are more likely to know letters in their own first names. Results indicate that both contextual factors have important impacts on measurement and that LNK does not meet the requirements of Rasch measurement even when accounting for the contextual factors. These findings introduce philosophical concerns for measurement of constrained skills which have limited content for assessment.     

Development of a comprehensiveness of Rasch measurement application scale

A large number of papers and technical reports are published every year describing researches where Rasch models are used. It has been observed, however, that not all the authors describe the application of the Rasch measurement with the same thoroughness. Some authors may leave behind important bits of information e.g. they may fail to investigate the person or item fit or may even fail to discuss the reliability of measurement. As a result, editorial guidelines have been published in order to suggest an informal minimum of thoroughness with which the authors may describe the application of Rasch measurement in their papers. This study presents stages for the development of a scale to investigate the comprehensiveness with which individual papers describe the application of Rasch models in practical settings. The scale is used to evaluate how comprehensively the papers published by the Journal of Applied Measurement present the application of Rasch models.     

Using the Rasch measurement model to investigate the construct of motor ability in young children

This paper reports the use of a Rasch measurement model, the Extended Logistic Model of Rasch (Andrich, 1988), to explore the construct of a general motor ability in young children. Data were collected from 332 five and six year old children performing 24 motor skills, including run, hop, balance and ball skills. The data were categorised based on threshold estimates provided by the measurement model. Gender differences in performances on items were hypothesised to contribute to initial item and person misfit for the total sample. The data for boys and for girls were separated and independently analysed resulting in improved item and person fit. Two different, unidimensional scales for boys and for girls were created.     

Rasch measurement in developing faculty ratings of students applying to graduate school

The Standardized Letter of Recommendation (SLR), a 28-item form, was created by ETS to supplement the qualitative rating of graduate school applicants' nonacademic qualities with a quantitative approach. The purpose of this study was to evaluate the following psychometric properties of the SLR using the Rasch rating scale model: dimensionality, reliability, item quality, and rating category effectiveness. Principal component and factor analyses were also conducted to examine the dimensionality of the SLR. Results revealed (a) two secondary factors underlay the data, along with a strong higher order factor, (b) item and person separation reliabilities were high, (c) noncognitive items tended to elicit higher endorsements than did cognitive items, and (d) a 5-point Likert scale functioned effectively. The psychometric properties of the SLR support the use of a composite score when reporting SLR scores and the utility of the SLR in higher education and in admissions.     

The Rasch model,additive conjoint measurement,and new models of probabilistic measurement theory

This research describes some of the similarities and differences between additive conjoint measurement (a type of fundamental measurement) and the Rasch model. It seems that there are many similarities between the two frameworks, however, their differences are nontrivial. For instance, while conjoint measurement specifies measurement scales using a data-free, non-numerical axiomatic frame of reference, the Rasch model specifies measurement scales using a numerical frame of reference that is, by definition, data dependent. In order to circumvent difficulties that can be realistically imposed by this data dependence, this research formalizes new non-parametric item response models. These models are probabilistic measurement theory models in the sense that they explicitly integrate the axiomatic ideas of measurement theory with the statistical ideas of order-restricted inference and Markov Chain Monte Carlo. The specifications of these models are rather flexible, as they can represent any one of several models used in psychometrics, such as Mokken's (1971) monotone homogeneity model, Scheiblechner's (1995) isotonic ordinal probabilistic model, or the Rasch (1960) model. The proposed non-parametric item response models are applied to analyze both real and simulated data sets.     

Mental self-government: development of the additional democratic learning style scale using Rasch measurement models

This paper describes the development and validation of a democratic learning style scale intended to fill a gap in Sternberg's theory of mental self-government and the associated learning style inventory (Sternberg, 1988, 1997). The scale was constructed as an 8-item scale with a 7-category response scale. The scale was developed following an adapted version of DeVellis' (2003) guidelines for scale development. The validity of the Democratic Learning Style Scale was assessed by items analysis using graphical loglinear Rasch models (Kreiner and Christensen, 2002, 2004, 2006) The item analysis confirmed that the full 8-item revised Democratic Learning Style Scale fitted a graphical loglinear Rasch model with no differential item functioning but weak to moderate uniform local dependence between two items. In addition, a reduced 6-item version of the scale fitted the pure Rasch model with a rating scale parameterization. The revised Democratic Learning Style Scale can therefore be regarded as a sound measurement scale meeting requirements of both construct validity and objectivity.     

The practical application of optimal appropriateness measurement on empirical data using Rasch models

Optimal Appropriateness Measurement (OAM) is a general statistical method for the identification of examinees whose test scores might not be a valid indicator of their true latent ability or trait. The method is statistically very powerful and it pinpoints towards the direction of the suspected aberrance instead of simply identifying that a specific response pattern is, in some way, aberrant. The method has been traditionally used with multi-parameter IRMs for the identification of examinees with spuriously low and high scores. This article presents the practical application of the method, using Rasch models, in the context of a large-scale activity which aimed to provide secondary education schools with feedback about their students' performance on a high-stakes University entrance science test. Although researchers in the past claimed that OAM was not ready to be routinely used in practical settings, this article maintains that the practical use of OAM to answer specific educationally meaningful questions is feasible.     

A Rasch analysis of three of the Wisconsin Scales of Psychosis Proneness: measurement of schizotypy

Rasch analyses were conducted with data from 90 university students on three of the Wisconsin Scales of Psychosis Proneness--the Magical Ideation (Eckblad & Chapman, 1983), Perceptual Aberration (Chapman, Chapman, & Raulin, 1978), and Revised Social Anhedonia Scales (Eckblad, Chapman, Chapman, & Mishlove, 1982). All of the items for each of the individual scales, plus all of the items from the combined Perceptual Aberration/Magical Ideation (Per-Mag) Scale, showed satisfactory fit to the Rasch model. These results show that personality traits including these psychosis proneness, or schizotypy, traits can be measured on a theoretically sound quantitative interval scale. Rasch scale equivalents for raw scores are provided. Possible improvements to the Magical Ideation, Perceptual Aberration, and Per-Mag scales are suggested by the item analysis. Advantages of Rasch scaling for clinical applications include detection of invalid test protocols, more meaningful interpretations of test scores, and direct comparison of scores from different tests of the same construct.     

Evidence for the reliability of measures and validity of measure interpretation: a Rasch measurement perspective

In an era of high stakes testing and evaluation in education, psychology, and health care, there is need for rigorous methods and standards for obtaining evidence of the reliability of measures and validity of inferences. Messick (1989, 1995), the Standard for Educational and Psychological Testing (American Psychological Association, American Educational Research Association, and National Council on Measurement in Education, 1999), and the Medical Outcomes Trust (1995), among others, have described methods that may be used to gather evidence for reliability and validity, but ignored the potential role Rasch measurement may contribute to this process. This article will outline methods in Rasch measurement that are used to gather evidence for reliability and validity and attempt to articulate how these methods may be linked with the current views of reliability and validity.     

Rasch measurement of self-regulated learning in an information and communication technology (ICT)-rich environment

This report describes how a linear scale of self-regulated learning in an ICT-rich environment was created by analysing student data using the Rasch measurement model. A person convenience sample of (N = 409) university students in Western Australia was used. The stem-item sample was initially 41, answered in two perspectives ("I aim for this" and "I actually do this"), and reduced to 16 that fitted the measurement model to form a unidimensional scale. Items for motivation (extrinsic rewards, intrinsic rewards, and social rewards), academic goals (fear of performing poorly) (but not standards), self-learning beliefs (ability and interest), task management (strategies and time management) (but not cooperative learning), Volition (action control (but not environmental control), and self-evaluation (cognitive self-evaluation and metacognition) fitted the measurement model. The proportion of observed variance considered true was 0.90. A new instrument is proposed to handle the conceptually valid but non-fitting items. Characteristics of high self-regulated learners are measured.     

Understanding the unit in the Rasch model

The purpose of this paper is to explain the role of the unit implicit in the dichotomous Rasch model in determining the multiplicative factor of separation between measurements in a specified frame of reference. The explanation is provided at two complementary levels: first, in terms of the algebra of the model in which the role of an implicit, multiplicative constant is made explicit; and second, at a more fundamental level, in terms of the classical definition of measurement in the physical sciences. The Rasch model is characterized by statistical sufficiency, which arises from the requirement of invariant comparisons within a specified frame of reference. A frame of reference is defined by a class of persons responding to a class of items in a well-defined response context. The paper shows that two or more frames of reference may have different implicit units without destroying sufficiency. Understanding the role of the unit permits explication of the relationship between the Rasch model and the two parameter logistic model. The paper also summarises an approach that can be used in practice to express measurements across different frames of reference in the same unit.     

Validation of scores from self-learning scales for primary students using true-score and Rasch measurement methods

The validation of scores from the Self-learning Scales for primary pupils is presented in this study. The sample for the study comprised 1253 pupils from 20 Year-3 and 20 Year-5 classes from ten primary schools in Hong Kong. The 10-item Usefulness Scale is designed to measure primary pupils' attitudes toward the usefulness of self-learning strategies situated in ten learning contexts. The 10-item Deployment Scale is designed to measure pupils' frequency in using the self-learning strategies. Both scales use 3-point Likert response scale. Construct validity of scores from the scales for use with primary pupils is supported by confirmatory factor analysis and Rasch measurement. Gender and year level differences were identified on the Rasch person measures. Generalizability of the scores from the two scales across gender and year level needs to be undertaken with caution.     

An approach to studying scale for students in higher education: a Rasch measurement model analysis

A questionnaire comprising 80 self-report items was designed to measure student Approaches to Studying in a higher education context. The items were conceptualized and designed from five learning orientations: a Deep Approach, a Surface Approach, a Strategic Approach, Clarity of Direction and Academic Self-Confidence, to include 40 attitude items and 40 corresponding behavior items. The study aimed to create a scale and investigate its psychometric properties using a Rasch measurement model. The convenience sample consisted of 350 students at an Australian university in 1998. The analysis supported the conceptual structure of the Scale as involving studying attitudes and behaviors towards five orientations to learning. Attitudes are mostly easier than behaviors, in line with the theory. Sixty-eight items fit the model and have good psychometric properties. The proportion of observed variance considered true is 92% and the Scale is well-targeted against the students. Some harder items are needed to improve the targeting and some further testing work needs to be done on the Surface Approach. In the Surface Approach and Clarity of Direction in Studying, attitudes make a lesser contribution than behaviors to the variable, Approaches to Studying.     

Double lateral shearing interferometer for the quantitative measurement of tear film topography

A lateral shearing interferometer designed and built for the study of the precorneal tear film topography dynamics and its effect on visual performance is presented. Simple data processing algorithms are discussed and tested on data illustrating different tear topography features: postblink tear undulation, tear breakup, eyelid-produced bumps and ridges, bubbles, and rough precontact lens tear surfaces.