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  • 11
    Electronic Resource
    Electronic Resource
    Nonmetric maximum likelihood multidimensional scaling from directional rankings of similarities (1981)
    Springer
    Psychometrika 46 (1981), S. 389-405 
    Details
    ISSN: 1860-0980
    Keywords: rank orders ; model selection ; AIC ; face perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract A maximum likelihood estimation procedure is developed for multidimensional scaling when (dis)similarity measures are taken by ranking procedures such as the method of conditional rank orders or the method of triadic combinations. The central feature of these procedures may be termed directionality of ranking processes. That is, rank orderings are performed in a prescribed order by successive first choices. Those data have conventionally been analyzed by Shepard-Kruskal type of nonmetric multidimensional scaling procedures. We propose, as a more appropriate alternative, a maximum likelihood method specifically designed for this type of data. A broader perspective on the present approach is given, which encompasses a wide variety of experimental methods for collecting dissimilarity data including pair comparison methods (such as the method of tetrads) and the pick-M method of similarities. An example is given to illustrate various advantages of nonmetric maximum likelihood multidimensional scaling as a statistical method. At the moment the approach is limited to the case of one-mode two-way proximity data, but could be extended in a relatively straightforward way to two-mode two-way, two-mode three-way or even three-mode three-way data, under the assumption of such models as INDSCAL or the two or three-way unfolding models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02293797
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    Paper (German National Licenses)
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  • 12
    Electronic Resource
    Electronic Resource
    Spatial versus tree representations of proximity data (1982)
    Springer
    Psychometrika 47 (1982), S. 3-24 
    Details
    ISSN: 1860-0980
    Keywords: multidimensional scaling ; clustering ; tree structures ; additive trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract In this paper we investigated two of the most common representations of proximities, two-dimensional euclidean planes and additive trees. Our purpose was to develop guidelines for comparing these representations, and to discover properties that could help diagnose which representation is more appropriate for a given set of data. In a simulation study, artificial data generated either by a plane or by a tree were scaled using procedures for fitting either a plane (KYST) or a tree (ADDTREE). As expected, the appropriate model fit the data better than the inappropriate model for all noise levels. Furthermore, the two models were roughly comparable: for all noise levels, KYST accounted for plane data about as well as ADDTREE accounted for tree data. Two properties of the data proved useful in distinguishing between the models: the skewness of the distribution of distances, and the proportion of elongated triangles, which measures departures from the ultrametric inequality, Applications of KYST and ADDTREE to some twenty sets of real data, collected by other investigators, showed that most of these data could be classified clearly as favoring either a tree or a two-dimensional representation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02293848
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Indclus: An individual differences generalization of the adclus model and the mapclus algorithm (1983)
    Springer
    Psychometrika 48 (1983), S. 157-169 
    Details
    ISSN: 1860-0980
    Keywords: additive clustering ; nonhierarchical clustering ; combinatorial optimization ; three-way clustering ; individual differences clustering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract We present a new model and associated algorithm, INDCLUS, that generalizes the Shepard-Arabie ADCLUS (ADditive CLUStering) model and the MAPCLUS algorithm, so as to represent in a clustering solution individual differences among subjects or other sources of data. Like MAPCLUS, the INDCLUS generalization utilizes an alternating least squares method combined with a mathematical programming optimization procedure based on a penalty function approach to impose discrete (0,1) constraints on parameters defining cluster membership. All subjects in an INDCLUS analysis are assumed to have a common set of clusters, which are differentially weighted by subjects in order to portray individual differences. As such, INDCLUS provides a (discrete) clustering counterpart to the Carroll-Chang INDSCAL model for (continuous) spatial representations. Finally, we consider possible generalizations of the INDCLUS model and algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02294012
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    Paper (German National Licenses)
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  • 14
    Electronic Resource
    Electronic Resource
    A maximum likelihood method for fitting the wandering vector model (1983)
    Springer
    Psychometrika 48 (1983), S. 553-566 
    Details
    ISSN: 1860-0980
    Keywords: preference ; paired comparisons data ; maximum likelihood multidimensional scaling ; method of successive categories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract After introducing some extensions of a recently proposed probabilistic vector model for representing paired comparisons choice data, an iterative procedure for obtaining maximum likelihood estimates of the model parameters is developed. The possibility of testing various hypotheses by means of likelihood ratio tests is discussed. Finally, the algorithm is applied to some existing data sets for illustrative purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02293879
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    Paper (German National Licenses)
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  • 15
    Electronic Resource
    Electronic Resource
    Synthesized clustering: A method for amalgamating alternative clustering bases with differential weighting of variables (1984)
    Springer
    Psychometrika 49 (1984), S. 57-78 
    Details
    ISSN: 1860-0980
    Keywords: Cluster Analysis ; Variable Importance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract In the application of clustering methods to real world data sets, two problems frequently arise: (a) how can the various contributory variables in a specific battery be weighted so as to enhance some cluster structure that may be present, and (b) how can various alternative batteries be combined to produce a single clustering that “best” incorporates each contributory set. A new method is proposed (SYNCLUS, SYNthesizedCLUStering) for dealing with these two problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02294206
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  • 16
    Electronic Resource
    Electronic Resource
    The estimation of ultrametric and path length trees from rectangular proximity data (1984)
    Springer
    Psychometrika 49 (1984), S. 289-310 
    Details
    ISSN: 1860-0980
    Keywords: Cluster Analysis ; Trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract A least-squares algorithm for fitting ultrametric and path length or additive trees to two-way, two-mode proximity data is presented. The algorithm utilizes a penalty function to enforce the ultrametric inequality generalized for asymmetric, and generally rectangular (rather than square) proximity matrices in estimating an ultrametric tree. This stage is used in an alternating least-squares fashion with closed-form formulas for estimating path length constants for deriving path length trees. The algorithm is evaluated via two Monte Carlo studies. Examples of fitting ultrametric and path length trees are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02306021
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    Paper (German National Licenses)
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  • 17
    Electronic Resource
    Electronic Resource
    Confidence regions for INDSCAL using the jackknife and bootstrap techniques (1984)
    Springer
    Psychometrika 49 (1984), S. 475-491 
    Details
    ISSN: 1860-0980
    Keywords: Individual differences ; multidimensional scaling ; stability ; standard errors ; pseudovalues ; maximum likelihood ; resampling schemes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract Bootstrap and jackknife techniques are used to estimate ellipsoidal confidence regions of group stimulus points derived from INDSCAL. The validity of these estimates is assessed through Monte Carlo analysis. Asymptotic estimates of confidence regions based on a MULTISCALE solution are also evaluated. Our findings suggest that the bootstrap and jackknife techniques may be used to provide statements regarding the accuracy of the relative locations of points in space. Our findings also suggest that MULTISCALE asymptotic estimates of confidence regions based on small samples provide an optimistic view of the actual statistical reliability of the solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02302586
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    Paper (German National Licenses)
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  • 18
    Electronic Resource
    Electronic Resource
    Hyperfine structure observed in EPR spectra of polyphenylacetylene solutions (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 1011-1020 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-temperature (〉120C) electron paramagnetic resonance (EPR) spectrum of solutions of polyphenylacetylene have been deconvoluted into the spectra of two separate radicals, a delocalized π radical, whose EPR spectrum consists of a single 15-G wide Gaussian line comprising about 90% of the total signal and a second, more localized π radical exhibiting complex hyperfine structure in its EPR spectrum. Some possible structures for the minor component radical are suggested and their hyperfine splitting constants calculated using molecular orbital theory.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190415
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    Paper (German National Licenses)
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