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Biomedical subjects

J Algina

Publications and source records attributed to J Algina.

9 recordsLinked to original sources
PubMed2001

Basal ganglia dysfunction, working memory, and sentence comprehension in patients with Parkinson's disease.

To investigate the role of the basal ganglia in working memory and sentence comprehension, 14 patients with Parkinson's disease (PD) were administered experimental measures of semantic and phonological working memory, and a measure of sentence comprehension, while receiving dopaminergic medications and after a period of withdrawal from these medications. An age- and education- matched control group (N=14) received the same measures. Comparison with control subjects revealed deficits in patients with PD in sentence processing regardless of medication status, but no deficits in working memory. In contrast to previous studies, withdrawal of dopaminergic medications had no significant impact on task- related working memory functions or on sentence comprehension. Results suggest that basal ganglia dysfunction does not solely account for sentence comprehension deficits seen in PD.

Aged↗
PubMed2001

The analysis of repeated measures designs: a review.

Repeated measures ANOVA can refer to many different types of analysis. Specifically, this vague term can refer to conventional tests of significance, one of three univariate solutions with adjusted degrees of freedom, two different types of multivariate statistic, or approaches that combine univariate and multivariate tests. Accordingly, it is argued that, by only reporting probability values and referring to statistical analyses as repeated measures ANOVA, authors convey neither the type of analysis that was used nor the validity of the reported probability value, since each of these approaches has its own strengths and weaknesses. The various approaches are presented with a discussion of their strengths and weaknesses, and recommendations are made regarding the 'best' choice of analysis. Additional topics discussed include analyses for missing data and tests of linear contrasts.

Analysis of Variance↗
PubMed2000

Measures of Effect Size for Comparative Studies: Applications, Interpretations, and Limitations.

Although dissatisfaction with the limitations associated with tests for statistical significance has been growing for several decades, applied researchers have continued to rely almost exclusively on these indicators of effect when reporting their findings. To encourage an increased use of alternative measures of effect, the present paper discusses several measures of effect size that might be used in group comparison studies involving univariate and/or multivariate models. For the methods discussed, formulas are presented and data from an experimental study are used to demonstrate the application and interpretation of these indices. The paper concludes with some cautionary notes on the limitations associated with these measures of effect size. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Testing treatment effects in repeated measures designs: trimmed means and bootstrapping.

Non-normality and covariance heterogeneity between groups affect the validity of the traditional repeated measures methods of analysis, particularly when group sizes are unequal. A non-pooled Welch-type statistic (WJ) and the Huynh Improved General Approximation (IGA) test generally have been found to be effective in controlling rates of Type I error in unbalanced non-spherical repeated measures designs even though data are non-normal in form and covariance matrices are heterogeneous. However, under some conditions of departure from multisample sphericity and multivariate normality their rates of Type I error have been found to be elevated. Westfall and Young's results suggest that Type I error control could be improved by combining bootstrap methods with methods based on trimmed means. Accordingly, in our investigation we examined four methods for testing for main and interaction effects in a between- by within-subjects repeated measures design: (a) the IGA and WJ tests with least squares estimators based on theoretically determined critical values; (b) the IGA and WJ tests with least squares estimators based on empirically determined critical values; (c) the IGA and WJ tests with robust estimators based on theoretically determined critical values; and (d) the IGA and WJ tests with robust estimators based on empirically determined critical values. We found that the IGA tests were always robust to assumption violations whether based on least squares or robust estimators or whether critical values were obtained through theoretical or empirical methods. The WJ procedure, however, occasionally resulted in liberal rates of error when based on least squares estimators but always proved robust when applied with robust estimators. Neither approach particularly benefited from adopting bootstrapped critical values. Recommendations are provided to researchers regarding when each approach is best.

Humans↗
PubMed1998

Efficacy of parent-child interaction therapy: interim report of a randomized trial with short-term maintenance.

Describes interim results of a study examining the effectiveness of parent-child interaction therapy (PCIT) with families of preschool-age children with oppositional defiant disorder. Following an initial assessment, 64 clinic-referred families were randomly assigned to an immediate treatment (i.t.) or a wait-list control (WL) condition. Results indicated that parents in the IT condition interacted more positively with their child and were more successful in gaining their child's compliance than parents in the WL condition. In addition, parents who received treatment reported decreased parenting stress and a more internal locus of control. Parents in the IT group reported statistically and clinically significant improvements in their child's behavior following PCIT. All families who received treatment reported high levels of satisfaction with both the content and process of PCIT. Preliminary 4-month follow-up data showed that parents maintained gains on all self-report measures.

Adult↗
PubMed1995

Parent-child interaction therapy: a psychosocial model for the treatment of young children with conduct problem behavior and their families.

This article describes a treatment project designed to examine the effectiveness and generalization of Parent-Child Interaction Therapy (PCIT) with families of preschool-aged children with conduct problem behavior. The importance of early intervention and issues related to measurement of change in these young children and their families are discussed. The treatment program and the study design are described, with particular emphasis on the measures used to assess treatment outcome. The sensitivity of the measures to change is illustrated with data from the first few families who have completed treatment.

Aggression↗
PubMed1994

Performance of four computer-based diagnostic systems.

BACKGROUND: Computer-based diagnostic systems are available commercially, but there has been limited evaluation of their performance. We assessed the diagnostic capabilities of four internal medicine diagnostic systems: Dxplain, Iliad, Meditel, and QMR. METHODS: Ten expert clinicians created a set of 105 diagnostically challenging clinical case summaries involving actual patients. Clinical data were entered into each program with the vocabulary provided by the program's developer. Each of the systems produced a ranked list of possible diagnoses for each patient, as did the group of experts. We calculated scores on several performance measures for each computer program. RESULTS: No single computer program scored better than the others on all performance measures. Among all cases and all programs, the proportion of correct diagnoses ranged from 0.52 to 0.71, and the mean proportion of relevant diagnoses ranged from 0.19 to 0.37. On average, less than half the diagnoses on the experts' original list of reasonable diagnoses were suggested by any of the programs. However, each program suggested an average of approximately two additional diagnoses per case that the experts found relevant but had not originally considered. CONCLUSIONS: The results provide a profile of the strengths and limitations of these computer programs. The programs should be used by physicians who can identify and use the relevant information and ignore the irrelevant information that can be produced.

Analysis of Variance↗
PubMedDate not supplied

Relationships among performance scores of four diagnostic decision support systems.

OBJECTIVE: To examine the relationships among different performance scores for each of four diagnostic decision support systems (DDSSs). DESIGN: Intercorrelations among seven performance scores on a set of 105 cases for each of four DDSSs (DXplain, Iliad, Meditel, QMR) were computed. METHODS: The performance scores for each case reflected: 1) presence or absence of the case diagnosis in the DDSS knowledge base; 2) presence or absence of the correct diagnosis anywhere on the DDSS diagnosis list; 3) presence or absence of the correct diagnosis in the top ten diagnoses; 4) relevance of the DDSS diagnosis list; 5) comprehensiveness of the DDSS diagnosis list; 6) whether the DDSS suggested additional diagnoses to the experts' list; and 7) the length of the DDSS diagnosis list. RESULTS: For all DDSSs, the two Correct Diagnosis scores (top ten and total list) were significantly related: 1) to the presence of the correct diagnosis in the knowledge base; 2) to the Comprehensiveness score; and 3) to each other. There were significant differences among the four DDSSs on the magnitude and/or direction of the relationships between: 1) the two Correct Diagnosis scores; 2) the Relevance and Length scores; and 3) the Relevance and Additional Diagnoses scores. CONCLUSION: The production of a correct diagnosis for a given case is not related to the number of diagnoses suggested by the DDSS and, across different DDSSs, is not consistently related to other measures of performance. These data indicate that multiple measures are needed to fully describe the performance of a DDSS.

Algorithms↗