PubMed Health⌕ Search

Biomedical subjects

N Cliff

Publications and source records attributed to N Cliff.

9 recordsLinked to original sources
PubMed2000

Increasing the reliability of Wechsler Intelligence Scale for Children--Third Edition difference scores with reliable component analysis.

Wechsler Intelligence Scale for Children--Third Edition index score differences are generally interpreted cautiously, if at all, primarily because of their poor reliability. On the basis of prior analyses with the Wechsler Adult Intelligence Scale--Third Edition (J. C. Caruso & N. Cliff, 1999), it was hypothesized that differences between scores defined by reliable component analysis would have higher reliability than those defined by traditional equal weighting. Differences between the reliable component scores showed substantially higher reliability than equally weighted score differences. The differences between reliable component scores were also substantially more reliable than those derived from the weighted scores suggested by K. C. H. Parker and L. Atkinson (1994). Using the weights provided in this article will allow researchers and practitioners to compute the RCA scores and have the assurance of high reliability with its attractive consequences.

Adolescent↗
PubMed2000

An examination of graduate students' statistical judgments: statistical and fuzzy set approaches.

The present study examined how statistical significance levels are treated and interpreted by graduate students who use hypothesis-testing in their scientific investigation. To test underlying psychological aspects of hypothesis-testing, the idea of fuzzy set theory was employed to identify the uncertain points in judgments. 34 graduate students in a psychology department made judgments about hypothetical statistical decisions. The results indicated that (1) the majority of these students treated significance levels on a continuum and rated them according to the magnitude of statistical significance; (2) the subjects shifted their decisions based on the types of hypothetical scenarios but not by the sample sizes; instead, they interpreted a smaller sample size as being less reliable. (3) The subjects frequently chose formally used statistical terms, e.g., Significant and Not Significant, more than graduated verbal expressions, e.g., Marginally Significant and Borderline Significant; and (4) the Fuzziness (degree of confidence in decision-making) was dependent on individuals and existed more in the critical points of transition where judgments are most difficult. The Fuzziness Index illustrated the subtle shifts of human decision-making patterns in statistical judgments. Underlying decision uncertainties and difficulties can be illustrated by functions generated from fuzzy set theory, which may more closely resemble human psychological mechanism. This integrative study of fuzzy set theory and behavioral measurements appears to provide a technique that is more natural for examining and understanding imprecise boundaries of human decisions.

Adult↗
PubMed1995

Redundant leading and following zeros in comparative numerical judgment.

The objective was to provide a more comprehensive understanding of how people make numerical comparative judgments when digits are contained in numbers with redundant leading or following zeros, e.g., 00080 and 800.000. These sequences of numbers often appear on computer display terminals (VDT) as line numbers, but surprisingly little research has been done on this. The experiment manipulated three aspects of numerical stimuli: (1) redundant leading zeros, (2) redundant following zeros, and (3) length of string of digits. The subjects were to push one of the two button-switches to respond whether two stimulus numbers shown on the computer screen were equal or unequal. The target stimuli contained several forms of redundant zeros, and each performance was assessed by response RT of the subjects. Analysis indicated five significant findings: (1) Redundant leading zeros hindered performance, (2) The effect of redundant following zeros depended on the stimulus type, (3) Over-all, longer digits took more processing time, (4) The RTs for the second-block trials were significantly faster than the first, and (5) Task performance was facilitated when the redundant zero representations were identical in both stimuli of a pair. Nonlexicographic processing seems to occur when feature identification can be used for numerical identification, that is, when the format is consistent. The research has implications for those in computer science to provide numerical formats which make comparative judgments as easy as possible.

Adult↗
PubMed1992

Principal components and multidimensional scaling of auditory and visual event-related potential topography.

Principal components analysis and metric multidimensional scaling were used to assess auditory and visual event-related potential topography in healthy late-middle-aged and elderly adults (n = 20). Binaurally elicited auditory evoked potentials and full-field checkerboard pattern reversal visual event-related potentials were recorded from 28 scalp sites. The zero-lag, cross-correlations of all waveforms for 300 msec post-stimulus epochs were obtained and separate analyses of the auditory and visual data were performed. Ultimately, three of the four dimensions identified in the principal components and multidimensional scaling solutions were similar and represented electrode site differences in (1) the anterior-posterior plane; (2) laterality; and, (3) the proximal-distal relation to midline. The remaining multidimensional scaling axis appeared to reflect effects specific to the modality of stimulation. Under auditory stimulation, the temporal and central-parietal sites were distinct from other scalp regions, whereas under visual stimulation, the occipital and frontal sites were distinctive. Although the results of the principal component analyses were conceptually similar to the multidimensional scaling outcomes, there were consistent differences between them. The findings provide empirical support for the validity of these multivariate methods in topographic analysis.

Acoustic Stimulation↗
PubMed1992

Analysis of pattern-reversal visual evoked-potential topography: replicability in normal subjects and comparisons with Alzheimer's disease.

This paper reports two studies using multivariate analysis to aid the interpretation of cross-coherence of multiple electrode sites in evoked potential responses. In the first study, the replicability of principal components and multidimensional scaling was evaluated by applying both methods to pattern-reversal visual evoked potentials recorded from 28 scalp sites in two subgroups of sex- and age-matched healthy subjects, and then comparing the results. Four dimensions replicated in the two initial multidimensional scaling solutions and appeared to reflect differences in: 1) anterior versus posterior scalp areas, 2) laterality, 3) separation of frontal and occipital sites from other scalp regions, and 4) proximal versus distal placements. The initial principal components did not match well in the two groups, but rotation to congruence improved their replicability and ultimately yielded axes similar to those of the multidimensional scaling dimensions. In the second study, Alzheimer's disease and sex- and age-matched control subjects were evaluated. The four axes identified were the same as those described above, but after the solutions were rotated to align them, the group differences appeared negligible. Examination of the components and dimensions from both studies showed some consistent departures from being merely reflectors of site location, and the apparently visual dimension appeared clearly in all four groups. Judged on the basis of initial interpretability and replicability of the solutions, the results suggest that multidimensional scaling, with appropriate transformation, may provide an effective tool for analyzing pattern-reversal visual evoked-potential topography.

Aged↗
PubMed1990

Using the longitudinal Guttman simplex as a basis for measuring growth.

Many difficulties inherent in the measurement of growth stem from the use of traditional measurement methodologies. The longitudinal Guttman simplex (LGS), an alternative approach based on a model of growth, is discussed in this article. The LGS has several advantages over traditional methodology. First, interindividual differences in developmental rates are a part of the model. Second, the LGS procedure can easily handle any number of occasions of measurement. Third, the LGS is suited to nonlinear as well as linear monotonic growth. Fourth, a consistency index associated with the LGS methodology, CL, indicates the extent to which cumulative, unitary development characterizes a particular latent variable. Finally, and perhaps most important, because a model of the growth undergone by the latent variable being measured is incorporated in the LGS model the resulting instruments enjoy a high level of construct validity. The LGS is limited to cumulative, unitary development; additional measurement theories are needed for other kinds of development.

Child↗