Biomedical subjects

G Karabatsos

Publications and source records attributed to G Karabatsos.

7 recordsLinked to original sources

PubMed2001

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.

Humans↗

PubMed2000

A critique of Rasch residual fit statistics.

In test analysis involving the Rasch model, a large degree of importance is placed on the "objective" measurement of individual abilities and item difficulties. The degree to which the objectivity properties are attained, of course, depends on the degree to which the data fit the Rasch model. It is therefore important to utilize fit statistics that accurately and reliably detect the person-item response inconsistencies that threaten the measurement objectivity of persons and items. Given this argument, it is somewhat surprising that there is far more emphasis placed in the objective measurement of person and items than there is in the measurement quality of Rasch fit statistics. This paper provides a critical analysis of the residual fit statistics of the Rasch model, arguably the most often used fit statistics, in an effort to illustrate that the task of Rasch fit analysis is not as simple and straightforward as it appears to be. The faulty statistical properties of the residual fit statistics do not allow either a convenient or a straightforward approach to Rasch fit analysis. For instance, given a residual fit statistic, the use of a single minimum critical value for misfit diagnosis across different testing situations, where the situations vary in sample and test properties, leads to both the overdetection and underdetection of misfit. To improve this situation, it is argued that psychometricians need to implement residual-free Rasch fit statistics that are based on the number of Guttman response errors, or use indices that are statistically optimal in detecting measurement disturbances.

Aptitude Tests↗

PubMed1999

Asthma: communication between hospital and general practitioners.

OBJECTIVE: To assess whether efforts to actively involve General Practitioners (GPs) in the postdischarge care of their paediatric asthma patients improved their satisfaction with communication with hospital staff. METHODOLOGY: Randomized controlled trial involving 60 patients admitted to the Royal Children's Hospital, Melbourne, with acute asthma and an identifiable GP. The GPs of the intervention patients were telephoned during the admission. Intervention patients and their GPs received printed information detailing the care the patient received in hospital and the recommended postdischarge care, as well as standardized educational booklets about asthma. Follow-up appointments were made for intervention patients to attend their GPs. RESULTS: The GPs of intervention patients were more satisfied when compared to the GPs receiving a standard level of communication (96.4% vs 48.3% of the intervention and control GPs, respectively, described the communication as good or extremely good, P = 0.0001). The intervention group GPs believed they were more involved after discharge (75.0% vs 44.8%, P = 0.005) and had greater understanding of their patient's hospitalisation (96.4% vs 62.1%, P = 0.005). These differences were noted despite there being no difference in the rate of follow-up attendance with GPs for intervention and control patients (85.7% vs 72.4%, P = 0.2). Qualitative data supported these findings with GPs expressing approval of the intervention used. CONCLUSION: Efforts to actively involve GPs in the postdischarge care of their paediatric patients with asthma resulted in a marked improvement in their satisfaction with the communication with medical staff at the Royal Children's Hospital, Melbourne. The study had insufficient power to demonstrate a difference in morbidity.

Aftercare↗

PubMed1999

Primer postcard improves postal survey response rates.

OBJECTIVE: This study measures the effect of an intervention to improve mailed survey response rates. METHOD: A randomised controlled trial of a 'primer' postcard was performed as part of a large survey in Victoria in 1997. Prior to the survey mailout, half the sample of 800 general practitioners supplied by the Health Insurance Commission was sent, at random, a primer card to request prompt return of the survey. RESULTS: The intervention resulted in a more rapid return of the survey and improved overall response rates from 60% to 66%. The increased cost per returned survey (40 cents) was largely offset by fewer non-responders requiring follow-up. CONCLUSIONS: A primer postcard is a time and cost-efficient method to increase response rates in general practitioner surveys. IMPLICATIONS: Public health researchers should consider implementing this intervention to improve response rates to postal surveys. Reports of other response maximising strategies should report the cost per returned survey to allow better comparison.

Attitude of Health Personnel↗

PubMed1998

Analyzing nonadditive conjoint structures: compounding events by Rasch model probabilities.

The following study proposes a Rasch method to measure variables of nonadditive conjoint structures, where dichotomous response combinations are evaluated. In this framework, both the number of endorsed items and their latent positions are considered. This is different from the cumulative response process (measurable by the Rasch model), where the probability of a positive response to an item with measure delta iota is considered a monotonic increasing function of the person's measure beta nu. This is also unlike the unfolding framework, where the probability of a positive response is maximum when beta nu = delta iota, and monotonically decreases as magnitude of beta nu-delta iota approaches infinity. The method involves four steps. In Step 1, items are scaled by the Rasch model for paired comparisons to produce a variable definition. These scale values serve as a basis for Steps 2 and 4. In Step 2, the nonadditive conjoint system is restructured to additive. The quantitative hypothesis of the restructured data is tested by the axioms of conjoint measurement theory in Step 3. This data is then analyzed by the Rasch rating scale model in Step 4 to evaluate individual response combinations, using the Step 1 item calibrations as anchors. The method was applied to simulated person responses of the Schedule of Recent Events (Holmes and Rahe, 1967). The results suggest that the method is useful and effective. It scales items with a robust method of paired comparisons, ensures additivity and quantification of the conjoint person-item matrix, produces a reasonable ordering of person measures from the perspective of individual response combinations, and provides satisfactory person and item separation (i.e., reliability). Furthermore, the restructured data reproduces SRE item scale values obtained by paired comparisons in Step 1.

Humans↗

PubMed1998

General practitioner involvement in hospital in the home. The hospital's view.

INTRODUCTION: Programs involving hospitals and general practitioners (GPs) have become more commonplace, with a greater emphasis on integration of health services emerging over the last generation. Hospital in the home (HIH) refers to the delivery of acute hospital services such as intravenous therapy, anticoagulation and wound care to patients in their own homes. This study sought to determine the extent to which HIH units had involved urban GPs, issues related to GP involvement, and the likely future of such involvement. METHOD: Telephone administered structured survey to all urban HIH coordinators/directors in Melbourne, Australia. RESULTS: All 14 identified HIH coordinators were interviewed. Five units reported a direct role for GPs, six reported no role and three reported a limited role in managing intercurrent illnesses. Coordinators felt that variability of GP response and skills, GP availability and patient control were significant issues. An increase in future GP involvement was uncertain and conditional. DISCUSSION: One-third of urban hospitals surveyed have involved GPs in their programs. However, issues such as variability in skills, enthusiasm and availability threaten expansion of such involvement. This calls for a review in the way GPs are involved in hospital programs, and for better relationships with hospital nursing staff. Limiting the number of involved GPs in any hospital-GP program may offer advantages to both groups. Despite the movement of hospital work into the community, GP involvement in such work is not guaranteed.

Family Practice↗

PubMed1997

The Sexual Experiences Survey: interpretation and validity.

The Sexual Experiences Survey (Koss, Gidycz, & Wisniewski, 1987) is a commonly used instrument for assessing various degrees of sexual aggression and victimization among male offenders and female victims. Rasch analysis was used to transform qualitative raw score observations into objective linear measures using the responses of a national sample of 6,159 higher education men and women across the United States, aged 18-24. This paper supports the construct validity of the survey through evaluation of the item hierarchy, fit statistics, and separation indices. Findings confirm a "dimensional" perspective on rape, suggesting that sexually aggressive behaviors can be scaled along a single continuum from normal to extreme sexual behavior. The item hierarchy reveals an arrangement of sexually aggressive acts in an order of mild to severe, which compares with the one theorized by the authors of the SES. Identity plots demonstrate the validity of using a common set of SES item calibrations to measure both male and female respondents. For interpretation of person responses to the SES, three conclusions are suggested. First, Rasch analysis must be employed to examine item responses effectively. Second, when the survey is administered to a college sample aged 18-24, the item calibrations obtained in this paper can be used to measure offenders and victims. Third, a total raw score-to-measure conversion is not always sufficient to interpret person measures. Instead, a scalogram method needs be added to the Rasch analysis to separate the measures of offenders and victims who complete the survey. Implications for future research are discussed.

Adult↗