175 research outputs found
Model-based Methods of Classification: Using the mclust Software in Chemometrics
Due to recent advances in methods and software for model-based clustering, and to the interpretability of the results, clustering procedures based on probability models are increasingly preferred over heuristic methods. The clustering process estimates a model for the data that allows for overlapping clusters, producing a probabilistic clustering that quantifies the uncertainty of observations belonging to components of the mixture. The resulting clustering model can also be used for some other important problems in multivariate analysis, including density estimation and discriminant analysis. Examples of the use of model-based clustering and classification techniques in chemometric studies include multivariate image analysis, magnetic resonance imaging, microarray image segmentation, statistical process control, and food authenticity. We review model-based clustering and related methods for density estimation and discriminant analysis, and show how the R package mclust can be applied in each instance.
Model-based Methods of Classification: Using the mclust Software in Chemometrics
Due to recent advances in methods and software for model-based clustering, and to the interpretability of the results, clustering procedures based on probability models are increasingly preferred over heuristic methods. The clustering process estimates a model for the data that allows for overlapping clusters, producing a probabilistic clustering that quantifies the uncertainty of observations belonging to components of the mixture. The resulting clustering model can also be used for some other important problems in multivariate analysis, including density estimation and discriminant analysis. Examples of the use of model-based clustering and classification techniques in chemometric studies include multivariate image analysis, magnetic resonance imaging, microarray image segmentation, statistical process control, and food authenticity. We review model-based clustering and related methods for density estimation and discriminant analysis, and show how the R package mclust can be applied in each instance
Least angle and penalized regression: A review
Least Angle Regression is a promising technique for variable selection
applications, offering a nice alternative to stepwise regression. It provides
an explanation for the similar behavior of LASSO (-penalized
regression) and forward stagewise regression, and provides a fast
implementation of both. The idea has caught on rapidly, and sparked a great
deal of research interest. In this paper, we give an overview of Least Angle
Regression and the current state of related research.Comment: Published in at http://dx.doi.org/10.1214/08-SS035 the Statistics
Surveys (http://www.i-journals.org/ss/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Adult romantic attachment: Theoretical developments, emerging controversies, and unanswered questions.
The experiences in close relationships—Relationship Structures Questionnaire: A method for assessing attachment orientations across relationships.
Region-Of-Interest Selection and Statistical Analysis of Dynamic Breast Magnetic Resonance Imaging Data
Magnetic Resonance Imaging (MRI) is emerging as a powerful tool for the diagnosis of breast abnormalities. Early investigation of contrast-enhanced MRI of the breast demonstrated that breast carcinoma consistently enhanced after the intravenous administration of contrast material (Gadolinium). However, many benign lesions also enhance reducing as a result MRI specificity- . Further characterization is necessary to differentiate benign from malignant lesions and analysis of the temporal pattern of contrast uptake has been applied to improve specificity. Selecting a Region-Of-Interest (ROI) is an almost universal step in the process of examining the contrast uptake characteristics of a breast lesion. A limitation of most ROI analysis procedures is that only subjectively selected regions are examined. We propose a ROI selection method based on techniques from multivariate data analysis and statistical image segmentation. In addition to the enhancement rate of the contrast material, we use other characteristics of the signal intensity to group areas of the breast with similar characteristics and then select the group which corresponds to a fast and strong enhancement. We then investigate tools for subsequent analysis of signal intensity time course data in the selected region in order to determine if the enhancing lesion is likely to be benign or malignant. We tested our procedure on cases for which the diagnosis was available. The results are promising and are consistent with the diagnosed nature of the lesions
Equivalence of Narcissistic Personality Inventory constructs and correlates across scoring approaches and response formats
The prevalent scoring practice for the Narcissistic Personality Inventory (NPI) ignores the forced-choice nature of the items. The aim of this study was to investigate whether findings based on NPI scores reported in previous research can be confirmed when the forced-choice nature of the NPI’s original response format is appropriately modeled, and when NPI items are presented in different response formats (true/false or rating scale). The relationships between NPI facets and various criteria were robust across scoring approaches (mean score vs. model-based), but were only partly robust across response formats. In addition, the scoring approaches and response formats achieved equivalent measurements of the vanity facet and in part of the leadership facet, but differed with respect to the entitlement facet
Idiopathic pulmonary fibrosis: Prognostic value of changes in physiology and six minute hallwalk.
Rationale and Hypothesis: Idiopathic pulmonary fibrosis is a fatal
disease with a variable rate of progression. We hypothesized that
changes in distance walked and quantity of desaturation during a
six-minute-walk test (6MWT) would add prognostic information to
changes in FVC or diffusing capacity for carbon monoxide.
Methods: One hundred ninety-seven patients with idiopathic pulmonary
fibrosis were evaluated. Desaturation during the 6MWT was
associated with increased mortality even if a threshold of 88%
was not reached. Baseline walk distance predicted subsequent walk
distance but was not a reliable predictor of subsequent mortality
in multivariate survival models. The predictive ability of serial
changes in physiology varied when patients were stratified by the
presence/absence of desaturation 88% during a baseline 6MWT.
For patients with a baseline saturation 88% during a 6MWT,
the strongest observed predictor of mortality was serial change in
diffusing capacity for carbon monoxide. For patients with saturation
88% during their baseline walk test, serial decreases in FVC
and increases in desaturation area significantly predicted subsequent
mortality, whereas decreases in walk distance and in diffusing
capacity for carbon monoxide displayed less consistent statistical
evidence of increasing mortality in our patients.
Conclusion: These data highlight the importance of stratifying patients
by degree of desaturation during a 6MWT before attributing
prognostic value to serial changes in other physiologic variables.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91940/1/2006 AJRCCM Idiopathic pulmonary fibrosis - Prognostic value of changes in physiology and six minute hallwalk.pd
Stability of Attachment Style in Adolescence: An Empirical Test of Alternative Developmental Processes
This is the peer reviewed version of the following article: Jones, J.D., Fraley, R.C., Ehrlich, K.B., Stern, J.A.,
Lejuez, C.W., Shaver, P.R. and Cassidy, J. (2018), Stability of Attachment Style in Adolescence: An Empirical
Test of Alternative Developmental Processes. Child Dev, 89: 871-880., which has been published in final form
at https://doi.org/10.1111/cdev.12775 . This article may be used for non-commercial purposes in accordance
with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced,
enriched or otherwise transformed into a derivative work, without express permission from Wiley or by
statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified.
The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing
or otherwise making available the article or pages thereof by third parties from platforms, services and websites
other than Wiley Online Library must be prohibited.Few studies have examined stability and change in attachment during adolescence. This 5-year longitudinal study (a) examined whether prototype or revisionist developmental dynamics better characterized patterns of stability and change in adolescent attachment (at T1, N = 176; M age = 14.0 years, SD = 0.9), (b) tested potential moderators of prototype-like attachment stability, and (c) compared attachment stability in adolescence to stability in adulthood. The results supported the prototype model, which assumes that there is a stable, enduring factor underlying stability and change in attachment. Exploratory moderation analyses revealed that family conflict, parental separation or divorce, minority status, and male sex might undermine the prototype-like stability of adolescent attachment. Stability of attachment was lower in adolescence relative to adulthood.https://doi.org/10.1111/cdev.1277
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