The purpose of the paper is to relate standard epidemiologic and statistical methods for measures of disease occurrence to the description of prevalence proportions and incidence rates of dental diseases. No new conce...
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The purpose of the paper is to relate standard epidemiologic and statistical methods for measures of disease occurrence to the description of prevalence proportions and incidence rates of dental diseases. No new concepts are introduced, but the choice of the unit of analysis of numerator and denominator is discussed, and the biological interpretation of the within-patient correlation coefficient is discussed.
The effectiveness of smoothing the bivariate distributions of common and noncommon item scores in the frequency estimation method of common-item equipercentile equating was examined. The mean squared error of equating...
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The effectiveness of smoothing the bivariate distributions of common and noncommon item scores in the frequency estimation method of common-item equipercentile equating was examined. The mean squared error of equating was computed for several equating methods and sample sizes, for two sets of population bivariate distributions of equating and nonequating item scores defined using data from a professional licensure exam. Eight equating methods were compared: five equipercentile methods and three linear methods. One of the equipercentile methods was unsmoothed equipercentile equating. Four methods of smoothed equipercentile (SEP) equating were considered: two based on log-linear models one based on the four-parameter beta binomial model, and one based on the four-parameter beta compound binomial model. The three linear equating methods were the Tucker method, the Levine Equally Reliable method, and the Levine Unequally Reliable method. The results indicated that smoothed distributions produced more accurate equating functions than the unsmoothed distributions, even for the largest sample size. Tucker linear equating produced more accurate results than SEP equating when the systematic error introduced by assuming a linear equating function was small relative to the random error of the methods of SEP equating.
The repetitive nature of the Zubair deltaic cycles, previously intuitively established, is quantitatively documented. The presence and extent of the Markov property is revealed by the application of a log-linear model...
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The repetitive nature of the Zubair deltaic cycles, previously intuitively established, is quantitatively documented. The presence and extent of the Markov property is revealed by the application of a log-linear model in conjunction with a stepwise procedure for identification of significant transitions. Three sets of contingency data tables, whose facies transitions are stepwise selected, are tested. Because of the varying rates of marine onlap exercised by the cycle's concluding phase, two sets, each consisting of a 4 × 4 matrix, were examined in order to assess the role of nearshore data on the repetitive nature of the sequence. The third set is a 12 × 12 matrix representing minor facies. The presence of a complete cycle, is nonetheless apparently unsupported by this analysis. Departure from quasi-independence is explained by either a single positive outlier (both sets of 4 × 4 matrices) or by the fact that a few transitions show statistically insignificant links (12 × 12 matrix), i.e., some transitions are a product of a random depositional process. Therefore, an intermediate model between the extremes of a random succession and a completely ordered cyclic succession is proposed. This type of cyclicity is probably the norm rather than the exception and is not due to partial lack of memory as much as to the frequent shifts and variable geographic extents assumed by sub-environments as they transgress time lines.
This paper reanalyses data from four nationally representative sample surveys, conducted in 1949, 1972, 1983 and 1987, to explore trends in class inequalities in education. log-linear models are used to test whether t...
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This paper reanalyses data from four nationally representative sample surveys, conducted in 1949, 1972, 1983 and 1987, to explore trends in class inequalities in education. log-linear models are used to test whether the relationship between father’s class and respondent’s education varies significantly by birth cohort. The conclusion is that the various educational reforms that have been attempted over the past 50 years in Britain have had little impact on class inequalities in education.
This article proposes an efficient numerical algorithm for small-sample exact inferences in contingency tables having ordinal classifications. The inferences, which apply conditional on the observed marginal totals, a...
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This article proposes an efficient numerical algorithm for small-sample exact inferences in contingency tables having ordinal classifications. The inferences, which apply conditional on the observed marginal totals, also provide an exact analysis for the log-linear model of linear-by-linear association for cell probabilities. An exact test of independence has a one-sided P value equal to the null probability that model-based maximum likelihood estimates of odds ratios are at least as large as the observed estimates. The conditional nonnull distribution yields confidence intervals for odds ratios having a linear-by-linear structure. The computations utilize an extension of the network algorithm proposed by Mehta and Patel (1983). [ABSTRACT FROM AUTHOR]
Lauritzen and Wermuth have proposed a class of models for mixed qualitative and continuous data, defined by two properties: that the continuous variables are normally distributed given the qualitative variables and th...
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Lauritzen and Wermuth have proposed a class of models for mixed qualitative and continuous data, defined by two properties: that the continuous variables are normally distributed given the qualitative variables and that a set of conditional independence relations hold between specified pairs of variables. These models, called graphical association models, include graphical log-linear models for contingency tables and covariance selection models for correlation matrices. The present paper examines an extension to this class called hierarchical interaction models. A compact form for model representation is described and an estimation algorithm is given. Some properties of the models concerning marginalization and conditioning are examined. The class includes and generalizes hierarchical log-linear models, standard fixed effect analysis of variance (ANOVA), multivariate ANOVA and multivariate regression models. Two applications are given.
Two populations (salt marsh and seagrass bed) of the hermit crab Pagurus longicarpus were sampled to examine associations between shell characteristics and egg production. Multivariate statistical analyses controlled ...
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Two populations (salt marsh and seagrass bed) of the hermit crab Pagurus longicarpus were sampled to examine associations between shell characteristics and egg production. Multivariate statistical analyses controlled for crab size and time of year, variables that otherwise could be confounded with shell effects. Although correlations between shell characteristics and reproduction existed in both populations, generalizations could not be made because associations varied within and between populations. Shell species was not associated with a female''s reproductive state (i.e., whether or not she was barren when sampled) in either population. In the seagrass population, medium-large and large females occupying severely damaged or fouled shells were half as likely to be reproductive as females occupying other shell conditions. However, there was no association between shell condition and reproductive state for small and small-medium females in the seagrass population or among all females in the salt marsh population. In the seagrass population, small through medium-large reproductive females occupied shells more similar to their predicted shell size, regardless of whether the occupied shell was relatively small or large, than nonreproductive females. In contrast, relative shell sizes of reproductive and nonreproductive females were similar for large females in the seagrass population and all females in the salt marsh population. Clutch sizes were enhanced for females occupying Polinices duplictus shells or shells larger than their predicted shell size in the seagrass population. Relative shell size also was associated with clutch size in the salt marsh population, but crabs occupying shells similar to their predicted shell size had the largest clutches.
We define and investigate classes of statistical models for the analysis of associations between variables, some of which are qualitative and some quantitative. In the cases where only one kind of variables is present...
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We define and investigate classes of statistical models for the analysis of associations between variables, some of which are qualitative and some quantitative. In the cases where only one kind of variables is present, the models are well-known models for either contingency tables or covariance structures. We characterize the subclass of decomposable models where the statistical theory is especially simple. All models can be represented by a graph with one vertex for each variable. The vertices are possibly connected with arrows or lines corresponding to directional or symmetric associations being present. Pairs of vertices that are not connected are conditionally independent given some of the remaining variables according to specific rules.
Discusses a study that established a class of expenditure functions for which a quadratic log-ratio system of demand equations is a viable formulation. Information on the resultant log-linear demand system; Details of...
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Discusses a study that established a class of expenditure functions for which a quadratic log-ratio system of demand equations is a viable formulation. Information on the resultant log-linear demand system; Details of the functional forms; Basic and parsimonious demand systems of structural equations.
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