Showing papers on "Matching (statistics) published in 1983"

The bias due to incomplete hatching

Abstract: Observational studies comparing groups of treated and control units are often used to estimate the effects caused by treatments. Matching is a method for sampling a large reservoir of potential controls to produce a control group of modest size that is ostensibly similar to the treated group. In practice, there is a trade-off between the desires to find matches for all treated units and to obtain matched treated-control pairs that are extremely similar to each other. We derive expressions for the bias in the average matched pair difference due to (1) the failure to match all treated units—incomplete matching, and (2) the failure to obtain exact matches—inexact matching. A practical example shows that the bias due to incomplete matching can be severe, and moreover, can be avoided entirely by using an appropriate multivariate nearest available matching algorithm, which in the example, leaves only a small residual bias due to inexact matching.

Planning and Analysis of Observational Studies

Abstract: Treats studies, primarily in human populations, that show casual effects of certain agents, procedures, treatment or programs. Deals with the difficulties that comparative observational studies have because of bias in their design and analysis. Systematically considers the many sources of bias and discusses how care in matching or adjustment of results can reduce the effects of bias in these investigations.

Matching images using linear features

Abstract: We describe techniques for matching two images or an image and a map. This operation is basic for machine vision and is needed for the tasks of object recognition, change detection, map up-dating, passive navigation, and other tasks. Our system uses line-based descriptions, and matching is accomplished by a relaxation operation which computes most similar geometrical structures. A more efficient variation, called the ``kernel'' method, is also described. We give results on complex aerial images which contain many image differences, caused by varying sun position, different seasons, and imaging environments, and also structural changes caused by man-made alterations such as new construction.

The double matching problem: Analytic and real frequency solutions

Abstract: A new and simplified analytic solution is given for the double matching problem. That problem requires the matching of a complex generator impedance to a complex load over a frequency band. The analytic solution is fundamental to understanding theoretical gain-bandwidth performance of systems but introduces severe difficulties when employed in design practice. Following the analytic presentation a CAD technique [the Real Frequency method] which bypasses the analytic theory and its difficulties of implementation is discussed. Various examples comparing the Real Frequency method to the analytic procedure are examined, It is shown that for double matching problems (as for single matching problems) the analytic method generally yields suboptimal performance characteristics. Thus just as in single matching problems, the Real Frequency method for double matching compared to the analytic procedure gives superior equalizer performance, simpler equalizer structures, and also is applicable to problems where the analytic method is virtually impossible to implement. As a final example the Real Frequency method is applied to the design of a two-stage microwave FET amplifier including input, output, and interstage equalizers.

Choice, matching, and human behavior: A review of the literature

Abstract: This review concerns human performance on concurrent schedules of reinforcement Studies indicate that humans match relative behavior to relative rate of reinforcement Herrnstein's proportional matching equation describes human performance but most studies do not evaluate the equation at the individual level Baum's generalized matching equation has received strong support with humans as subjects This equation permits the investigation of sources of deviation from ideal matching and a few studies have suggested variables which control such deviations in humans While problems with instructional control are raised, the overall findings support the matching law as a principle of human choice

Matching, maximizing, and hill-climbing

Abstract: In simple situations, animals consistently choose the better of two alternatives. On concurrent variable-interval variable-interval and variable-interval variable-ratio schedules, they approximately match aggregate choice and reinforcement ratios. The matching law attempts to explain the latter result but does not address the former. Hill-climbing rules such as momentary maximizing can account for both. We show that momentary maximizing constrains molar choice to approximate matching; that molar choice covaries with pigeons' momentary-maximizing estimate; and that the "generalized matching law" follows from almost any hill-climbing rule.

Strategic selection: matching executives to business conditions.

Abstract: Each business situation requires that executives have a specific set of management skills and characteristics to make the business successful. As businesses adapt their strategies and organizational structures to a changing environment, this set of managerial characteristics must also change: a company may discover its executives are not as suited to manage under the new conditions as they were under the old. The authors contend that executive selection should be linked to strategy, and they present a framework for assessing the managerial characteristics required by various strategic business situations.

Generating Models of Solid Objects by Matching 3D Surface Segments.

Abstract: This paper summarizes a method for constructing surface models of arbitrarily-shaped, solid objects by spatially matching 3D surface segments describing the objects. A surface segment of a solid object is a partial description of the object's surface, usually limited to the surface area that can be reconstructed from two corresponding images of the object in an arbitrary orientation. Each surface segment is defined in its 3D coordinate system. The matching algorithm uses heuristic search to align overlapping surface segments of an object into a common 3D coordinate system. It searches for a rigid 3D transformation which minimizes shape differences between a pair of surface segments. Once this transformation is determined, the surface segments are merged into a new segment. This match-and-merge process is iteratively repeated for pairs of available surface segments until a complete model of the object is assembled.

Scene Matching by Hierarchical Correlation

Abstract: : In this paper the authors present an implementation of hierarchical scene matching in the VISIONS image processing cone - a pyramidal processing architecture. The problem of scene matching is common to many applications in machine vision including registration, motion detection, and stereo vision. Scene matching by feature correlation can solve this problem but suffers from computational expense and failure in highly textured images. Hierarchical correlation provides both a cheaper matching algorithm and a coarse-to-fine matching strategy that overcomes textural problems by matching on gross image structures first. These methods fit naturally into the processing cone or pyramid architectures that have been proposed for image processing. Presented is a discussion of the architecture of the processing cone, the construction of image pyramids, and the use of these pyramids in hierarchical correlation. A set of experiments illustrates the operation of these ideas.

Parallel text matching methods and apparatus

Abstract: Pattern-matching circuitry is shown which permits the simultaneous or near simultaneous matching of entire lines of text to a regular expression test pattern A synchronous or clocked embodiment is disclosed, as well as an asynchronous embodiment

Apparatus and method for compression of facsimile information by pattern matching

Abstract: A technique and apparatus for facsimile encoding wherein patterns isolated in each incoming image or picture are compared against stored library patterns, and an identification number associated with a matching pattern and its location in the facsimile are encoded in place of a pixel-by-pixel pattern description. The library of stored patterns used for matching purposes is organized such that frequently occurring patterns are examined early in the matching process, decreasing processing time. Identification numbers associated with matched patterns on each scanning line are numerically sorted, so that the ID's can be differentially encoded. At any time during pattern matching, detection of significant differences between the incoming pattern and a particular library pattern generates a reject decision, immediately terminating that match attempt. If desired features of the incoming patterns can be compared to library pattern features, using tight and then loose screening criteria, in order to preselect patterns used in the matching process.

Linguistic determinants of bias in conditional reasoning

Abstract: An experiment is reported to test the hypothesis that a non-logical tendency known as “matching bias”, which occurs in conditional reasoning tasks, is linguistically determined. It is argued that t...

A review of the use of inverted files for best match searching in information retrieval systems

Abstract: The use of inverted files for the calculation of similarity coefficients and other types of matching function is discussed in the context of mechanised document retrieval systems. A critical evaluation is presented of a range of algorithms which have been described for the matching of documents with queries. Particular attention is paid to the computational efficiency of the various procedures, and improved search heuristics are given in some cases. It is suggested that the algorithms could be implemented sufficiently efficiently to permit the provision of nearest neighbour searching as a standard retrieval option.

Choice, experience, and the generalized matching law.

Abstract: Five pigeons were exposed to different pairs of concurrent variable-interval, variable-interval schedules on nine experimental conditions of 30 sessions each. For every session, the parameters of the generalized matching equation were computed for the first five, six, seven, eight, and nine experimental conditions. The exponent a, both for response and time distribution, tended to decrease with increases in number of experimental conditions and to increase with number of sessions per condition, but values of k (bias) varied unsystematically. When the subjects were exposed to five new pairs of schedules, with 55 sessions per condition, the findings were confirmed. Data from the literature on the generalized matching law suggest that the variability of exponent values may be explained in part by the use of naive or experienced subjects in different investigations and by the variability in number of experimental conditions and in number of sessions per condition.

Indicators of Adoption Breakdown

Abstract: Eighty cases of adoption breakdown were compared with a control group of successful adoptions. An analysis of placement decisions strongly indicated that matching a marginal child with marginal par...

Signal detection and matching: analyzing choice on concurrent variable‐interval schedules

Abstract: Pigeons' pecks on a red key and a green key were followed by access to grain according to pairs of concurrent independent variable-interval schedules in a combined signal detection/matching law paradigm. Pecks on the red key were reinforced by the richer variable-interval schedule if a short-duration tone had been presented; pecks on the green key were reinforced by the richer variable-interval schedule if a long-duration tone had been presented. Pecks on the green key given a short-duration tone, or on the red key given a long-duration tone, were reinforced by the leaner variable-interval schedule. The data were analyzed according to both signal detection's and the matching law's separate measures of, first, the discrimination of the choices and, second, the bias to make one response or another. Increasing the difficulty of the tone-duration discrimination decreased both methods' measures of the discrimination of the choices and did not change both methods' measures of the bias to make one response or another. Changing the leaner variable-interval schedule so that it approached the richer variable-interval schedule decreased signal detection's measure of discrimination but left its measure of response bias and the matching law measures unchanged. Data collected only until a subject's first changeover response following presentation of a long or a short tone showed higher values for both methods' measures of discrimination, no change in signal detection's measure of response bias, and lower values for the matching law's measure of response bias. Relationships between the matching law's and signal detection's methods of analyzing choice are discussed. It is concluded that a signal detection analysis is more efficient for examining changes in the difficulty of a discrimination, whereas a matching law analysis is more effective for examining the effects of changes in relative reinforcer frequency.

External Validity of Matching on Physical Attractiveness for Same and Opposite Sex Couples1

Abstract: The external validity of the hypothesis that couples come to be matched on physical attractiveness was examined for same and opposite sex pairs of college students in a wide range of natural settings and types of relationships. Correlations between ratings of couples by observers revealed evidence of matching for male friends and for opposite sex friends, dating, and committed couples. No evidence was found for female friends. The implications of these findings for fear of social rejection and exchange explanations of the matching hypothesis and for the normal development of interpersonal relationships are discussed.

Hierarchical file organization and its application to similar-string matching

Abstract: The automatic correction of misspelled inputs is discussed from a viewpoint of similar-string matching. First a hierarchical file organization based on a linear ordering of records is presented for retrieving records highly similar to any input query. Then the spelling problem is attacked by constructing a hierarchical file for a set of strings in a dictionary of English words. The spelling correction steps proceed as follows: (1) find one of the best-match strings which are most similar to a query, (2) expand the search area for obtaining the good-match strings, and (3) interrupt the file search as soon as the required string is displayed. Computational experiments verify the performance of the proposed methods for similar-string matching under the UNIX™ time-sharing system.

*SIM Competition Paper:* The Application Approach Worksheet: An Evaluative Tool for Matching New Development Methods with Appropriate Applications

Abstract: This article presents a method used by the Hennepin County Information Services development staff to determine how best to use new development methods. The tool described and the method for using it were designed to help both data processing personnel and user personnel make the transition from using one development approach only, to a variety of approaches using new technologies and methods. In brief, the \"Application Approach Worksheet\" is a document used by mid-level and senior user management to identify, in data processing terms, the characteristics of a proposed application. Once the application's characteristics are defined, the user utilized the worksheet's matrix to determine which development might by most appropriate for the application. The completed worksheet and a work request then becomes the basis to propose development of the new application. At that point, an Information Services Department (ISD) project manger discusses the application with the user. Together, they agree on the project's priority relative to other projects, and work out how the project will be handled in general. This article first describes the environment in which the \"Application Approach Worksheet\" was developed and the circumstances that led to its development. The article goes on to discuss how the worksheet was created and describes the criteria that form the heart of the document. Finally, the article describes how the worksheet is used and discusses the results of its use since it became a part of the work request process in January of 1983.

Matching Elastic Templates

Abstract: This paper describes a new efficient algorithm for elastic template matching. The algorithm is based on a coarse to fine matching strategy which iteratively improves the correspondence between images. The high cost of elastic matching is greatly reduced by incorporating efficient techniques for image representation and search. Recognition accuracy of 99% was achieved when using the elastic technique for handprinted character recognition.

Methodological Issues in Case-Control Studies: Validity and Power of Various Design/Analysis Strategies

Abstract: Computer stimulations have been used to estimate the efficiency, as measured by the statistical power, of various combinations of design and analysis strategies for case-control studies. Conditions under which the various forms of analysis yield consistent relative risk estimators are derived for the general model. The results indicate that the loss of efficiency resulting from the use of a less than optimum design or analysis strategy in many real life situations is small. Practical considerations are of more importance than theoretical statistical ones in deciding upon appropriate strategies. It is concluded that matching is rarely, if ever, justified in most case-control studies of chronic diseases.