Showing papers on "Matching (statistics) published in 1987"

Hedonic Prices and Implicit Markets: Estimating Demand and Supply Functions for Differentiated Products

Abstract: In choosing the level of quality to purchase, the buyer of a differentiated product also chooses a point on the marginal price schedule for that product. Hence, in general, the demand functions for product characteristics cannot be consistently estimated by ordinary least squares. Market equilibrium results in a matching of characteristics of demanders and suppliers. This matching restricts the use of buyer and seller characteristics as instruments when estimating demand and supply functions for product characteristics. The paper develops these issues. A stochastic structure for hedonic equilibrium models is then proposed, identification results are presented, and estimation procedures are outlined.

Sensitivity analysis for certain permutation inferences in matched observational studies

Abstract: SUMMARY In observational studies, treatments are not randomly assigned to experimental units, so that randomization tests and their associated interval estimates are not generally applicable. In an effort to compensate for the lack of randomization, treated and control units are often matched on the basis of observed covariates; however, the possibility remains of bias due to residual imbalances in unobserved covariates. A general though simple method is proposed for displaying the sensitivity of permutation inferences to a range of assumptions about unobserved covariates in matched observational studies. The sensitivity analysis is applicable to Wilcoxon's signed rank test, to the McNemar-Cox test for paired binary responses, and to some matching problems with a variable number of controls.

An efficient algorithm for the “optimal” stable marriage

Abstract: In an instance of size n of the stable marriage problem, each of n men and n women ranks the members of the opposite sex in order of preference. A stable matching is a complete matching of men and women such that no man and woman who are not partners both prefer each other to their actual partners under the matching. It is well known [2] that at least one stable matching exists for every stable marriage instance. However, the classical Gale-Shapley algorithm produces a marriage that greatly favors the men at the expense of the women, or vice versa. The problem arises of finding a stable matching that is optimal under some more equitable or egalitarian criterion of optimality. This problem was posed by Knuth [6] and has remained unsolved for some time. Here, the objective of maximizing the average (or, equivalently, the total) “satisfaction” of all people is used. This objective is achieved when a person's satisfaction is measured by the position of his/her partner in his/her preference list. By exploiting the structure of the set of all stable matchings, and using graph-theoretic methods, an O(n4) algorithm for this problem is derived.

Identification of partially obscured objects in two and three dimensions by matching noisy characteristic

Abstract: In this paper we analyze the problem of matching partially obscured, noise-corrupted images of composite scenes in two and three dimensions. We describe efficient methods for smoothing the noisy da...

Signal matching through scale space

Abstract: Given a collection of similar signals that have been deformed with respect to each other, the general signal-matching problem is to recover the deformation. We formulate the problem as the minimization of an energy measure that combines a smoothness term and a similarity term. The minimization reduces to a dynamic system governed by a set of coupled, first-order differential equations. The dynamic system finds an optimal solution at a coarse scale and then tracks it continuously to a fine scale. Among the major themes in recent work on visual signal matching have been the notions of matching as constrained optimization, of variational surface reconstruction, and of coarse-to-fine matching. Our solution captures these in a precise, succinct, and unified form. Results are presented for one-dimensional signals, a motion sequence, and a stereo pair.

Brain Potentials as Indices of Orthographic and Phonological Interaction During word Matching

Abstract: The interaction between orthographic and phonological codes in a same-different judgment task was studied by requiring subjects to decide if two visually presented words either looked alike or rhymed. Word pairs were selected from four different lists. Words rhymed and looked alike, rhymed but did not look alike, looked alike but did not rhyme, or neither looked alike nor rhymed. Reaction time and percent error increased whenever there was a conflict between the orthography and phonology of the words. The N200 component of the event-related brain potential (ERP) indicated that subjects were capable of detecting phonological differences between words within 260 ms from the presentation of a word pair. The amplitude of the N200s also varied with the degree of mismatch between words. N200s were largest when both the orthography and phonology mismatched, of intermediate amplitude when either orthography or phonology mismatched, and smallest when both orthography and phonology matched. P300 latency was consistent with reaction time, increasing whenever there was a conflict between the two codes. Taken together, behavioral measures and the ERP data suggest that the extraction of the orthographic and phonological aspects of words occurs early in the information processing sequence.

The Flypaper Effect Revisited: An Econometric Explanation

Abstract: Monte Carlo evidence is presented which supports the conclusion that when a block grants variable in an ordinary least squares (OLS) model is endogenously constructed due to the closed-ended nature of matching aid, estimates of the propensity to spend lump-sum aid are biased upward. The findings suggest that OLS estimates lead to erroneous conclusions regarding the existence of a flypaper effect and support the use of maximum likelihood models in situations where budget constraints are piecewise-linear.

Temporal resource variability and the habitat-matching rule

Abstract: The ideal free distribution of competitors in a heterogeneous environment often predicts habitat matching, where the equilibrium number of consumers in a patch is proportional to resource abundance in that patch. We model the interaction between habitat matching and temporal variation in resource abundance. In one patch the rate of resource input follows a Markov chain; a second patch does not vary temporally. We predict patch use by scaling transition rates in the variable patch to the time that consumers require to respond to changes in rates of resource input. If consumers respond very quickly, habitat matching tracks temporal variability. If resource input fluctuates faster than consumers respond, habitat matching averages over the equilibrium of the Markov chain. Tracking and averaging produce the same mean resource consumption for individuals, but long-term mean occupation of the patches differs. When habitat matching tracks temporal variability in resources, consumer density in the variable patch has a lower mean and a higher variance than when habitat matching reflects only average rates of resource input.

The Use of Coloured Overlays to Improve Visual Processing ‐ A Preliminary Survey

Abstract: Forty volunteers reporting consistent reading problems were divided into three groups on the basis of an assessment of degree of scotopic sensitivity. Four speeded visual processing tasks involving word matching and letter and number identification were administered to all subjects using three plastic overlays, one of a colour maximizing visual efficiency, one chosen at random and one with no colour. For subjects with high scotopic sensitivity, the use of optimal coloured overlays yielded significantly better results on some visual tasks than the other two overlays. Implications of these findings are discussed.

Method and apparatus for matching panels to be cut from patterned fabrics

Abstract: A matching method and apparatus for the automatic cutting of patterned fabrics by an integrated marking and cutting system first defines matching points in each of the patterns of panels to be cut and digitizes these points so that the coordinates and respective identification codes for each of the points are recorded in a memory. Matching relationships are then defined for the matching points which unequivocally fix the position which the design must be in at each of the matching points and digitizes and records these relationships in the memory. Separation margins between the panels in their distribution are then established either automatically or interactively on the basis of the previously defined matching relationships and a vision sensor is then automatically positioned over the spread patterned fabric which is to be cut in the positions of the matching points which have been defined for each one of the panels which have been distributed for cutting. The relative design position with respect to a reference position at each of the matching point positions is then determined and a position correction obtained for each panel with respect to the position initially assigned to each one of the panels to be cut, each position correction being obtained on the basis of the positions of the pattern determined in the previous step and on the basis of the previously defined matching relationships wherein all of the panels which are to be cut are matched prior to proceeding with their cutting operation.

HERMeS: A second generation approach to the automatic analysis of two‐dimensional electrophoresis gels. Part III: Spot list matching

Abstract: One of the most critical steps in two-dimensional gel analysis is the comparison of spot lists. In this paper, we describe our approach to the matching problem. We propose a method based on syntactic pattern recognition techniques, which differs from previously used methods and offers a major improvement to cope with discontinuous geometric distortions. The method is based on non-metric considerations and describes the pattern observed on a given gel in a non-geometric way. This approach leads to the definition of finite automatons which can be used to automatically find the presence of a given pattern on a gel. The program uses a technique of clause generation related to artificial intelligence techniques. A set of rules is applied to the definition of homologousspots, and probability coefficients are computed to compare and to chose between different pairing hypotheses. Once matching has been achieved between a set of gels, the construction of a master gel which summarizes the information obtained is allowed. Two types of masters can be used. The first one summarizes the information between spots lists belonging to the same experiment and includes intensity considerations, while the second one summarizes the information resulting from different gels and does not include spot intensity and volume. Masters are written and known by the system as a spot list. This ability allows them to be handled just like spot lists and, using them, to perform all the actions available to the system. This approach is compared with a more classical one based on geometric corrections. The use of probability coefficients is also discussed and extended to their application to multiple matching and further utilization of masters.

Complexity in classificatory reasoning

Abstract: Classificatory reasoning involves the tasks of concept evaluation and classification, which may be performed with use of the strategies of concept matching and concept activation, respectively. Different implementations of the strategies of concept matching and concept activation are possible, where an implementation is characterized by the organization of knowledge and the control of information processing it uses. In this paper we define the tasks of concept evaluation and classification, and describe the strategies of concept matching and concept activation. We then derive the computational complexity of the tasks using different implementations of the task-specific strategies. We show that the complexity of performing a task is determined by the organization of knowledge used in performing it. Further, we suggest that the implementation that is computationally the most efficient for performing a task may be cognitively the most plausible as well.

Pied piping and the matching parameter

Abstract: A number of scholars most recently, Suner (1984) have considered and offered analyses for some or all of the following facts concerning '(non-) matching effects' (with respect to Case and category) in F(ree) R(elative) constructions: (I) Some languages allow unrestricted non-matching (e.g. Latin, Classical, Greek, Gothic); others allow non-matching under certain conditions only (Finnish, Catalan, Spanish, Rumanian); and others disallow nonmatching in general (French, English). Let us call these three types (a), (b), and (c) respectively. The first and the last three (b)-type languages mentioned above have been characterized in past literature in different ways; Finnish, in terms of a hierarchy of Case-markedness (Bresnan and Grimshaw 1978: section 6), and the three Romance languages, äs allowing nonmatching in subject and L(eft)-D(islocation) position only (Hirschbühler and Rivero 1981, 1983; Suner 1984; Horvath and Grosu 1987). We will refer to the latter subtype äs (b'). (II) Some languages have matching effects in all argument positions, but not in LD position (German). (III) Some languages allow matching PP-initiated FRs in general (Spanish, French, Rumanian), others allow such FRs only for certain PPs (English, according to Bresnan and Grimshaw 1978), and others allow such FRs under no circumstances (German, Dutch). (IV) Some languages (Spanish, Rumanian, Hebrew, Russian) exhibit (what is usually not quite correctly characterized äs) 'infinitival' FRs, and these unlike the 'tensed' variety are always free from matching effects. While partly written in the form of a reexamination of the proposals made in Suner (1984) in relation to (I)-(IV), this paper first and foremost addresses a number of issues of general interest; in particular, whether pro in head-of-FR position can be identified ¥R-externally9 whether the two above-mentioned subtypes of (b) are really different, and whether infini-

Patents, Citations and Innovations: Tracing the Links

Abstract: The goal is to tackle anew the main problems encountered in using patent data in economic research, namely, the large variance in the value of patents, and the difficulties in matching patents with economic categories. The first is addressed with the aid of patent citations, the second with computerized search techniques for large databases. The proposed solutions are applied to the case of Computed Tomography (CT) Scanners, a pathbreaking innovation in medical technology. The main findings are that patents weighted by citations are highly correlated with the value of innovations, and that important innovations generate further innovative activity (R&D), and hence bring about down-the-line patents.

On Analytic Empirical Bayes Estimation of Failure Rates

Abstract: The estimation of plant accident rates and component failure rates is addressed within the framework of a parametric empirical Bayes approach. The observables, the numbers of failures recorded in various similar systems, obey the Poisson probability law. The parameters of a common gamma prior distribution are determined by a special moment matching method such that the results are consistent with classical (fiducial) confidence limits. Relations between Bayesian, classical, and Stein's estimation are discussed. The theory of the method is fully developed, although the suggested procedure itself is relatively simple. Solutions exist and they are in allowed ranges for all practical cases, including small samples and clustered data. They are also unbiased for large samples. Numerical examples are analyzed to illustrate the method and to allow comparisons with other methods.

Matching and portfolio selection: Part 2

Abstract: 8.1 This paper is concerned with the selection of investment portfolios to meet specified criteria which involve the liabilities of a long term investing institution such as a pension fund or a life office. In Part 1 (5) I showed a certain relationship between, on the one hand, portfolios selected according to a criterion of pure matching to the liabilities and, on the other hand, portfolios selected according to a more general criterion of ‘efficiency’. This connection points to a particular actuarial approach to the selection of portfolios, which is now further examined in Part 2.8.2 Writing Part 2 separately presents an opportunity to re-state the main ideas. The next few paragraphs recapitulate the basic points with a view to reducing, within the subsequent discussion, the amount of cross-reference to Part 1, and to the three preceding papers on which the study is based.

Evaluating the Impact of CETA on Participant Earnings.

Abstract: This article summarizes estimates of CETA net impact on labor market outcomes using multivariate matching and weighting. The approach produces a comparison group from the Current Population Survey similar to the treatment sample on higher order interactions of match variables and displays only limited sensitivity to model specification. Unlike other approaches that rely on a priori assumptions, the estimates do not require explicit assumptions concerning the temporary or permanent nature of the "preentry earnings dip. "Statistical tests show the resulting comparison groups to be superior both to random samples of eligibles from the Current Population Survey and to comparison groups derived by statistical matching without replacement. Consistent with program changes, FY 1977 impact estimates were higher than FY 1976 impact estimates.

Use of magnitude matching for measuring group differences in pain perception

Abstract: a Mon 2:30 Room 1 Aim of investigation: Psychophysics of nociception were for long me a n a substantial model of experimental pruritus. The study quantifies the properties of iontophoresis of a natural itch mediator, histamine. Methods: Histamine +ions were delivered to the skin of the ventral forearms of 22 volunteers of both sexes using 10s constant current pulses. Stimulus size was calculated as charge (time x current). For the purpose of psychophysics 5 levels of stimulation of 0.156-0.625-2.5 and 10 mC plus one zero control stimulus were applied in random order. SubJects calibrated to the session by means of a medium sized stimulus (1.25 mC). Itch sensations developing usually within seconds were reported by the subjects via discrete ratings of a visual analogue scale (VAS). The objective skin reactions of wheal and flare were measured by planimetry and laser Doppler flowmetry (Periflux PF2) (flux), respectively. Results: VAS ratings of perceived itch sensation gave correlation coefficients of r=0.45 with respect to logarithm of stimulus strength. Analysis of variance revealed a significant2 impact of the factors “stimulus intensity”, “sex” and “subjects” (p

Basic processes in reading: On the development of cross-case letter matching without reference to phonology

Abstract: We report the case of a youngster who has not learned to name correctly all of the letters of the alphabet, but who nonetheless can do cross-case matching (Posner’s name-matching task) of all the letters, entirely without error. This result suggests that the development of cross-case matching abilities in normal subjects may also proceed without reference to a letter identification process based upon a phonological code.

Labour Market Participation in Matching Equilibrium

Abstract: This paper uses ideas developed recently in models of equilibrium search to consider the participation decision of workers who have different preferences for leisure. The matching process is random, the production process deterministic, and wages are determined by a Nash bargain among participants. In steady-state equilibrium, the number of participants is inefficient due to externalities resulting from private decisions. A condition for efficient worker participation is derived which turns out also to be the condition for efficient firm entry. Copyright 1987 by The Review of Economic Studies Limited.