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111.
When do infants begin to communicate positive affect about physical objects to their social partners? We examined developmental changes in the timing of smiles during episodes of initiating joint attention that involved an infant gazing between an object and a social partner. Twenty‐six typically developing infants were observed at 8, 10, and 12 months during the Early Social‐Communication Scales, a semistructured assessment for eliciting initiating joint attention and related behaviors. The proportion of infant smiling during initiating joint attention episodes did not change with age, but there was a change in the timing of the smiles. The likelihood of infants smiling at an object and then gazing at the experimenter while smiling (anticipatory smiling) increased between 8 and 10 months and remained stable between 10 and 12 months. The increase in the number of infants who smiled at an object and then made eye contact suggests a developing ability to communicate positive affect about an object. 相似文献
112.
113.
James P. McDermott G. Jogesh Babu John C. Liechty Dennis K. J. Lin 《Statistics and Computing》2007,17(4):311-321
We consider the problem of density estimation when the data is in the form of a continuous stream with no fixed length. In
this setting, implementations of the usual methods of density estimation such as kernel density estimation are problematic.
We propose a method of density estimation for massive datasets that is based upon taking the derivative of a smooth curve
that has been fit through a set of quantile estimates. To achieve this, a low-storage, single-pass, sequential method is proposed
for simultaneous estimation of multiple quantiles for massive datasets that form the basis of this method of density estimation.
For comparison, we also consider a sequential kernel density estimator. The proposed methods are shown through simulation
study to perform well and to have several distinct advantages over existing methods. 相似文献
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115.
Constrained allocation problems with single-peaked preferences: An axiomatic analysis 总被引:1,自引:0,他引:1
Özgür Kıbrıs 《Social Choice and Welfare》2003,20(3):353-362
We introduce a new class of problems that contains two existing classes: allocation problems with single-peaked preferences
and bankruptcy problems. On this class, we analyze the implications of well-known properties such as Pareto optimality, strategy-proofness,
resource-monotonicity, no-envy, equal treatment of equals, and two new properties we introduce, hierarchical no-envy and independence
of nonbinding constraints. Unlike earlier literature, we consider rules that allow free-disposability. We present characterizations
of a rule we introduce on this domain. We relate this rule to well-known rules on the aforementioned subdomains. Based on
this relation, we present a characterization of a well-known bankruptcy rule called the constrained equal awards rule.
Received: 22 June 2000/Accepted: 21 March 2002
This paper is based on the first chapter of my Ph.D. thesis submitted to the University of Rochester. I wish to thank my
advisor, William Thomson, for helpful comments and suggestions. 相似文献
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It is often of interest to find the maximum or near maxima among a set of vector‐valued parameters in a statistical model; in the case of disease mapping, for example, these correspond to relative‐risk “hotspots” where public‐health intervention may be needed. The general problem is one of estimating nonlinear functions of the ensemble of relative risks, but biased estimates result if posterior means are simply substituted into these nonlinear functions. The authors obtain better estimates of extrema from a new, weighted ranks squared error loss function. The derivation of these Bayes estimators assumes a hidden‐Markov random‐field model for relative risks, and their behaviour is illustrated with real and simulated data. 相似文献
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120.
This article examines the effect third-party certification has on a market characterized by adverse selection. Using an original data set from the market for young thoroughbreds, we show that certification alleviates problems of adverse selection by examining the effect certification has on breeder decisions to retain or sell horses and the effect these decisions have on observed prices. Data on the racetrack performance of the horses confirm the results. 相似文献