The changing relationship between class and political party in Britain has been the subject of considerable debate among social scientists, much of it about the measures used to identify patterns of change. The paper ...
详细信息
The changing relationship between class and political party in Britain has been the subject of considerable debate among social scientists, much of it about the measures used to identify patterns of change. The paper updates previous work by extending it to the most recent British election, by comparing different procedures for allocating respondents to classes, and by using a recently developed log-multiplicative ('UNIDIFF“) model which is especially appropriate for testing whether or not classes have converged in their voting behaviour. The analysis confirms and strengthens previous interpretations which have argued that the class basis of partisanship is not in continuing decline.
Preparatory brain activity from frontal, centro-lateral, and occipital areas were recorded from top-level rifle shooters during shooting performance. The aim of the study was to examine the relation of brain slow pote...
详细信息
Preparatory brain activity from frontal, centro-lateral, and occipital areas were recorded from top-level rifle shooters during shooting performance. The aim of the study was to examine the relation of brain slow potentials to qualitative (rifle holding) and quantitative (hit) aspects of superior shooting performance. For this purpose, a typology of slow potentials (SPs) was developed. The resulting SP types were used for unraveling the associations between the electrocortical activity and behavioral output. The main finding was that frontal positivity was associated with successful performance, but only if the central-right SP was more negative than the central-left one. This finding was explained as showing that, in the case of superior performance, a shooter is able to refrain from irrelevant motor activity (frontal positivity) and concomitantly concentrate on the visual-spatial processing (right-sided negativity). In all, the present experiment suggests that the SPs are consistently related to the covert aspects of shooting performance, which lack an overt manifestation. At the practical level, this means that the SPs provide a tool for accessing information concerning the optimal balance between visual-spatial targeting and motor activity which can make a valuable contribution to the understanding of superior shooting performance.
We proposed simplified formulas for computing the standard errors of equipercentile equating for continuous and discrete test scores. The suggested formulas are conceptually simple and easily extended to more complica...
详细信息
We proposed simplified formulas for computing the standard errors of equipercentile equating for continuous and discrete test scores. The suggested formulas are conceptually simple and easily extended to more complicated equating designs such as chained equipercentile equating, smoothed equipercentile equating, and equating using the frequency estimation method. Results from an empirical study indicate that the derived formulas work reasonably well for samples with moderate sizes (e.g., 1,000 examinees).
We develop models for three-dimensional contingency tables containing both completely and partially cross-classified data for which one of the variables is regarded as dependent and the other two variables are regarde...
详细信息
We develop models for three-dimensional contingency tables containing both completely and partially cross-classified data for which one of the variables is regarded as dependent and the other two variables are regarded as independent variables. Parameters of interest include the cell probabilities and the probabilities that the observations on one or both independent variables are missing. The models allow inferences on these two sets of probabilities to be made independently. Maximum likelihood methods for estimating and testing hypotheses regarding these parameters are described, along with conditional goodness-of-fit test statistics, which display a convenient additivity property. The methodology is applied to cervical cancer data from a case-control study performed in Atlanta, Georgia, 1985-1988.
The distribution and abundance of Enchytraeidae and Tubificidae in and around Spartina alterniflora plants in a tidal salt marsh on Sapelo Island, Georgia, USA were studied using two different sampling techniques: wet...
详细信息
The distribution and abundance of Enchytraeidae and Tubificidae in and around Spartina alterniflora plants in a tidal salt marsh on Sapelo Island, Georgia, USA were studied using two different sampling techniques: wet funnel extraction and stem dissection. At least 80 % of all worms inhabited leaf sheaths at the bases of S. alterniflora plants, and densities were low in sediment, root and surface debris samples. Oligochaete densities were dependent on the position within the marsh, the height on stems and the stage of sheath decay. Six predominant species were identified and included Marionina appendiculata, Marionina spartinae, Marionina waltersi, Marionina paludis, and Monopylephorus parvus. Individual species were distributed differently on stems and enchytraeids were more common than tubificids on standing-dead and further up S. alterniflora stems. Estimates of oligochaete densities in salt marsh habitats are increased dramatically when the numbers of worms on stems are considered. Possible advantages of the stem microhabitat are discussed in relation to the biology and ecology of oligochaetes.
Suppose we are given n independent observations (X1, Y1), ..., (X(n), Y(n)) from a conditionally specified distribution with density f(x,y). The problem of estimating the unknown parameters of f(x,y) is complicated by...
详细信息
Suppose we are given n independent observations (X1, Y1), ..., (X(n), Y(n)) from a conditionally specified distribution with density f(x,y). The problem of estimating the unknown parameters of f(x,y) is complicated by the presence of an intractable normalizing constant that, in this conditional approach, is chosen so that the density integrates to 1. An approach to estimation is used here that is known to result in asymptotically efficient estimators of the unknown parameters when f(x,y) is from an exponential family. It is an application of a method that has appeared in the literature and is due to J. K. Lindsey. It very conveniently avoids the dependence on the normalizing constants in the joint distribution. The usual maximum-likelihood estimates of the parameters can be obtained using software readily available for Poisson regression. The usefulness of this estimation method is illustrated for a model resulting from specifying that the conditionals are two-parameter, shape and scale, gamma. It is assumed that only the scale parameter depends on the conditioning variable. This model subsumes the BEC class and several characteristics of the model extend those of the BEC class.
When modeling intraspecific relationships between selected measurements (Y) for differences in body mass (m) using the allometric equation Y = am(b) (where a is a constant and b is the exponent parameter), various stu...
详细信息
When modeling intraspecific relationships between selected measurements (Y) for differences in body mass (m) using the allometric equation Y = am(b) (where a is a constant and b is the exponent parameter), various studies have reported exponents greater than the anticipated 2/3, Often closer to the exponent 0.75 identified by Kleiber. A possible explanation for these exponents is proposed based on the findings of Alexander et al. (J. Zool. Lend. 194: 539-552, 1981), who observed that, within a variety of species, larger mammals have a greater proportion of proximal leg muscle mass in relation to their body mass, m(1.1). If subjects that are used to record Y exhibit a similar disproportionate increase in muscle mass with body size, then the allometric equation is likely to identify both a contribution proportional to the subject's body mass and a contribution from the disproportionate increase in muscle mass within the group. These confounding influences in Y can be identified separately by incorporating a body size parameter as well as a mass component in the allometric equation. The factor ''body size'' can be introduced either by partitioning the sample into discrete subgroups according to body size or, in studies involving human subjects, by introducing height as a continuous covariate. In both studies reported involving human maximal exercise, these methods were able to identify a systematic increase in Y with body size, leaving the subject's body mass component, found to be proportional to m(2/3), independent of body size.
This case-study outlines the important stages that needed to be addressed when formulating a regression model to explain health-related variables, such as maximum oxygen uptake, taken from the Allied Dunbar national f...
详细信息
This case-study outlines the important stages that needed to be addressed when formulating a regression model to explain health-related variables, such as maximum oxygen uptake, taken from the Allied Dunbar national fitness survey. Relevant references suggested two competing models. A nonlinear regression model, originally proposed to predict forced expiratory volume, appeared to be equally suitable for predicting the estimated maximum oxygen uptake. However, the parsimonious solution was found to be inexplicable on physiological grounds, as well as providing heteroscedastic and non-normal residuals. An alternative weighted log-linear regression model, containing a proportional body weight and a negative exponential age term, was then considered. This model gave more plausible and precise parameter estimates which had a generally lower level of intercorrelation. The log-linear model also gave less evidence of multicollinearity and the residuals were found to be acceptably normal. Finally, a bootstrap comparison of likelihoods confirmed the log-linear model to be superior.
When mark-recapture data are analysed by log-linear models, as described by Cormack (1989, Biometrics 45, 395-413), the analysis is in terms of parameters that are related nonlinearly to the parameters of biological i...
详细信息
When mark-recapture data are analysed by log-linear models, as described by Cormack (1989, Biometrics 45, 395-413), the analysis is in terms of parameters that are related nonlinearly to the parameters of biological interest. For several models formulae are given expressing the variance of the interesting parameter estimates in terms of those provided by a computer log-linear analysis. A device is presented that allows such expressions to be computed simply.
A model specified in terms of linearmodels for marginal logits and linearmodels for log-odds ratios is proposed for the analysis of two-period binary cross-over experiments. Hypothesis testing and parameter estimati...
详细信息
A model specified in terms of linearmodels for marginal logits and linearmodels for log-odds ratios is proposed for the analysis of two-period binary cross-over experiments. Hypothesis testing and parameter estimation are facilitated by standard likelihood methodology. Two examples are used to illustrate how the model can be used to analyze two-period binary cross-over experiments. Results from a simulation study demonstrate that this approach to the analysis of binary cross-over data compares favorably with standard procedures, such as the Mainland-Gart test for a treatment difference, Prescott's test for a treatment difference, and the Hills-Armitage test for treatment-by-period interaction.
暂无评论