Physical Sciences and Mathematics Commons^™

Who Enrolled In A State Program For The Uninsured: Was There Adverse Selection?, Paula Diehr

Paula Diehr

Managed care plans may hesitate to participate in programs for uninsured persons because they fear adverse selection, whereby only the sickest people or highest users would choose to join the program. We studied this issue in Washington State's Basic Health Plan, a demonstration program that provides subsidized health insurance for families earning less than 200% of the poverty level. We interviewed people in three counties who enrolled in the program, and compared them to people in the same counties who were eligible but did not enroll. There were substantial differences between enrollees and eligibles in education, age, income, employment, race, …

Solving The Ranking And Selection Indifference-Zone Formulation For Normal Distributions Using Computer Software, Catherine A. Poston

Theses and Dissertations

Ranking and selection procedures are statistical methods used to compare and choose the best among a group of similar statistically distributed populations. The two predominant approaches to solving ranking and selection problems are Guptas subset selection formulation and Bechhofers indifference- zone formulation. For the indifference-zone formulation where the populations have equal sample sizes, Barr and Rizvi developed an integral expression of the probability of correct selection PCS. Given appropriate parameters, the integral expression can be solved to determine the common sample size required to attain a desired PCS. Tables with selected solutions to the integral expression are available for a …

Reproducibility Of Periodontal Probing, Su-Fang Wang

Loma Linda University Electronic Theses, Dissertations & Projects

This study evaluated reproducibility of periodontal probing by conventional manual and automated force-controlled electronic probes. A total of 1206 sites (6 sites per tooth including maxillary and mandibular incisor/canine, premolar, and molar sites) in 15 patients with history of moderate or advanced chronic periodontal disease were examined. Probings included probing pocket depths (PD), as well as probing attachment levels (PAL) from a reference stent. Measurements were recorded to the nearest 0.5 mm with both methods. Patients were examined twice, 7 to 10 days apart. At each visit, all sites were probed first with the conventional probe and then with the …

Developing Prediction Regions For A Time Series Model For Hurricane Forecasting, William Cheman

Theses and Dissertations

In this thesis, a class of time series models for forecasting a hurricanes future position based on its previous positions and a generalized model of hurricane motion are examined and extended. Results of a literature review suggest that meteorological models continue to increase in complexity while few statistical approaches, such as linear regression, have been successfully applied. An exception is provided by a certain class of time series models that appear to forecast storms almost as well as current meteorological models without their tremendous complexity. A suggestion for enhancing the performance of these time series models is pursued through an …

Deadly Confusion: Juror Instructions In Capital Cases, Theodore Eisenberg, Martin T. Wells

Cornell Law Faculty Publications

A fatal mistake. A defendant is sentenced to die because the jury was misinformed about the law. The justice system should be designed to prevent such a tragic error. Yet our interviews with jurors who served in South Carolina capital cases indicate that this nightmare is a reality.

Although our data are limited to South Carolina, the question whether jurors are adequately instructed in capital cases is of national concern. For example, the issue whether jurors should be more fully informed about the alternative to a death sentence has arisen in other states. And the question whether jurors understand the …

Controllability And Stabilizability Of Coupled Strings With Control Applied At The Coupled Points, Lop-Fat Ho

Mathematics and Statistics Faculty Publications

Controllability and stabilizability of a system of coupled strings with control applied at the coupled points is studied. By investigating the properties of certain exponential series, it is shown that the system is approximate controllable if and only if related systems of uncoupled strings do not share a common eigenvalue. A sufficient condition for exact controllability is also obtained in terms of the Riesz basis properties of those exponential series.

Do Communities Differ In Health Behaviors?, Paula Diehr

Paula Diehr

Communities differ in the prevalence of various health behaviors, but it is not known to what extent these differences are due to "different types" of people living in them. We used data from the evaluation of the Henry J Kaiser Family Foundation Community Health Promotion Grant Program to study individual-level and community-level variation in health behaviors for 15 communities. Our results show (1) there was significant variation among these communities in prevalences of smoking, consumption of alcohol and dietary fat, and use of seatbelts; (2) these differences persisted after control for demographic, health status, and other health behavioral characteristics of …

Harmonic-Analysis Of Fractal Measures Induced By Representations Of A Certain C*-Algebra, Palle Jorgensen, Steen Pedersen

Mathematics and Statistics Faculty Publications

We describe a class of measurable subsets Ω in R^d such that L²(Ω) has an orthogonal basis of frequencies e_λ(x) = e^i2πλ.x(x ε Ω) indexed by λ ∈ Λ ⊂ R^d. We show that such spectral pairs (Ω, Λ) have a self-similarity which may be used to generate associated fractal measures μ with Cantor set support. The Hilbert space L²(μ) does not have a total set of orthogonal frequencies, but a harmonic analysis of mu may be built instead from a natural representation of the Cuntz …

Student Fact Book, Fall 1993, Wright State University, Office Of Student Information Systems, Wright State University

Wright State University Student Fact Books

The student fact book has general demographic information on all students enrolled at Wright State University for Fall Quarter, 1993.

The Efficiency Of The College Football Betting Market For Southeastern Conference Teams, Ravija Badarinathi, Ladd Kochman

Faculty and Research Publications

To illustrate economic testing and at the same time to conduct an inquiry into the efficiency of the college football betting market, an analysis applies all the betting rules reported by Stark (1992) to the 10 teams comprising the Southeastern Conference before the recent addition of the universities of Arkansas and South Carolina. The combination of 10 teams and 7 conditions produces a total of 70 betting strategies. Since each rule to bet for a team is shadowed by the alternative of betting against that team, the actual number of rules tested is 140. Among those 140 rules, only 7 …

Approximation Methods For Singular Diffusions Arising In Genetics, Nacer E. Abrouk

Mathematical Sciences Technical Reports (MSTR)

Stochastic models in population genetics leading to diffusion equations are considered. When the drift and the square of the diffusion coefficients are polynomials, an infinite system of ordinary differential equations for the moments of the diffusion process can be derived using the Martingale property. An example is provided to show how the classical Fokker-Planck Equation approach may not be appropriate for this derivation. A Gauss-Galerkin method for approximating the laws of the diffusion, originally proposed by Dawson (1980), is examined. In the few special cases for which exact solutions are known, comparison shows that the method is accurate and the …

A Non-Human Primate Model For Evaluating A Fenestration Corticotomy Technique, Philip G. M. Khng

Loma Linda University Electronic Theses, Dissertations & Projects

A study model has been designed to evaluate the effectiveness of a new fenestration corticotomy procedure in two non-human primates Macaca fasicularis.

The objective of this study was to evaluate the efficacy of a new conservative corticotomy procedure to facilitate dental translation using fenestrations. This pilot study compared treatment and control quadrants of each individual animal's maxilla and mandible with both having the same retraction appliance and force on the 2nd premolar following extraction of the 1st molars. The null hypothesis stated that there was no significant statistical difference between the new conservative corticotomy procedure (fenestrations) when compared with …

The Impact Of A Primary Health Care Training Program On Morbidity In Kiyeyi, Rural Uganda, 1986-1991 : An Evaluation Of The Uganda-Finland Health Care Program, Marja-Leena Salin

Loma Linda University Electronic Theses, Dissertations & Projects

This study examines the effects of primary health care education efforts in reducing the disease case rates of acute respiratory infections, diarrhoea, malnutrition and measles in a rural Ugandan population between 1986 and 1991.

The intervention, a health education program offered by the Kiyeyi Health Center staff, consisted of a 12-week intensive training for community health workers and traditional birth attendants. Follow-up and supervision took place at regular intervals and continuing education was arranged every other year. Beginning in 1986, this training program was introduced in the first of seven clusters of villages, then expanded successively on an annual basis …

Small Area Variation Analysis. Methods For Comparing Several Diagnosis-Related Groups., Paula Diehr

Paula Diehr

In small-area variation analysis, the variation of health care utilization rates, e.g., admission rates, among small areas is calculated. Frequently, the variation of one diagnosis, diagnosis-related group (DRG), or procedure is compared with the variation of another. Unfortunately, the methods generally used to make these comparisons are not consistent. They differ on whether they 1) adjust for the prevalence of the DRGs, 2) distinguish between variation among areas and variation within areas, 3) weight all areas equally, and 4) adjust for multiple admissions per person. None has an associated confidence interval. These discrepancies occur in part because there is no …

Diet And Colon Cancer Risk In The Population Of Thailand, Nithat Sirichotiratana

Loma Linda University Electronic Theses, Dissertations & Projects

Epidemiological studies have emphasized environmental influences, especially a diet high in animal fat and low in fiber, as major risk factors for colon cancer. In order to examine the relationship between dietary fat and fiber and occurrence of colon cancer, patient medical records from the National Cancer Institute between 1981-1991 were used for the first hospital-based case-control study of diet and colon cancer in Thailand. These records included a total of 168 cases and 357 controls. Data on the frequency consumption of various food items were obtained by using an existing food frequency questionnaire, completed as part of patient’s history …

Can Simple Random Sampling Confidence Intervals Be Used On Transect Sampling Data?, William Noble

Conference on Applied Statistics in Agriculture

When sampling geographic regions, transect sampling may be easier and cheaper than simple random sampling. However, transect sampling data is more difficult to analyze. In the past, transect sampling data has sometimes been analyzed as if it was the result of simple random sampling. The purpose of this note is to present simulation results which show that this can lead to vastly inaccurate conclusions when one is calculating confidence intervals. In particular, an example is given of a purported 95% confidence interval which is actually a 49% confidence interval.

Binomial Variation In The Sex Composition Of Pig Families, Thomas Kirchoff, D. F. Cox

Conference on Applied Statistics in Agriculture

Given the known mechanisms for sex determination, the number of males in families of pigs should follow a binomial distribution. A report of deviations from binomial expectation prompted an investigation of 33,176 pig records from two breeds collected on a single farm. Two methods of assessing the agreement with the binomial distribution found no evidence of significant lack of fit.

A Permutation Test For A Repeated Measures Design, James J. Higgins, William Noble

Conference on Applied Statistics in Agriculture

Multivariate permutation tests have advantages over conventional methods in analyzing repeated measures designs. The tests are exact for all sample sizes regardless of the underlying population distribution from which the observations are selected. More importantly the tests do not require a priori assumptions about the form of the correlation structure, obviating the need to check Huynh-Feldt conditions. An example is given of how a multivariate permutation test may be conducted in a context frequently encountered in agricultural research. The SAS program corresponding to this example is also given.

Litter Mate Correlations In The Weight Of Pigs, Thomas Kirchoff, D. F. Cox

Conference on Applied Statistics in Agriculture

Competition may influence the weights of animals confined to litters or pens, if conditions occur that limit the space and the feed provided, by inducing a negative correlation among the weights within the groups. An example of the phenomenon appeared in the birthweight of pigs where the intra-class correlation declined in a linear manner with increasing litter size. The data consisted of records on 33,165 pigs from 3282 litters raised on a single farm.

Overcoming Resistance To Multivariate Analysis Over Time, April J. Milliken, Anne M. Parkhurst

Conference on Applied Statistics in Agriculture

One aspect of statistical consulting is assessing a clients needs. Sometimes the need for simplicity beclouds the information contained in the experiment. As an example, an experiment was performed as a multivariate study with repeated measures, yet the client preferred numerous univariate analyses that ignored time. The challenge was to show how a more sophisticated analysis provided additional insight into the biological process. Various covariance structures were employed to illustrate the usefulness of progressively more complex analyses. Multivariate methods were performed to utilize the correlation among variables to illuminate biological concepts. To complicate the whole process, an additional problem occurred …

A Comparison Of Algorithms For Selecting An Optimum Sample From H Strata Using K Variables, M. Williams, H. T. Schreuder

Conference on Applied Statistics in Agriculture

In stratified sampling with k different variables and H strata it is often of interest to minimize the survey cost with respect to variance restrictions on each of the k variables. This problem has previously been solved using compromise solutions or using a linear approximation to this nonlinear problem. In this paper a nonlinear optimization routine is tested on this problem. The formulation of the problem in its original form proved problematic. For the test cases run, the transformation t_h = l/n_h, where n_h is the number of samples in stratum h, performed best when k …

Imputing Characteristic Values Of Agricultural "Seed-Stock", Bbryan E. Melton, W. Arden Colette, Richard L. Willham

Conference on Applied Statistics in Agriculture

Statistical methods of regression and mathematical (linear) programming are employed to combine principles of economics and genetics in a conceptual, multi-step, model of valuation for biotechnical change. The resulting model has the capacity to estimate the value of changes in specific characteristics for specific production environments, whether those changes are accomplished by traditional plant and animal breeding methods or by genetic engineering. The application of the model is illustrated with an example of commercial cow-calf production under conditions typical of the Texas Panhandle using a total of 32 breed groups.

Fuzziness In Forest Survey Design Optimization, George Gertner, Xiangchi Cao

Conference on Applied Statistics in Agriculture

When using optimization techniques to optimize a sampling with partial replacement design, it is often assumed that the following parameters are known exactly: 1) desired level of sampling error or total sampling cost for the survey; 2) variable costs; and 3) population variance and correlation coefficients. In practice, however, these parameters needed for finding the optimal design are only educated guesses. The parameters can be considered to be fuzzy. In this paper, brief consideration is given to the optimization of a sampling with partial replacement design using nonlinear programming techniques with fuzzy parameters. The basis of this method is to …

The Effect Of Weather Station Density On Crop Yield Forecasts, M. Denice Mccormick

Conference on Applied Statistics in Agriculture

The National Agricultural Statistics Service (NASS) uses regression models to forecast yield for crops such as corn, soybeans and winter wheat. Analyses were conducted on the use of precipitation data in these regression models (McCormick and Birkett 1992, and McCormick 1993). Precipitation data are obtained from two sources. The National Climatic Data Center (NCDC) supplies historic precipitation data used for developing regression model parameters. The Climate Analysis Center (CAC) supplies current year precipitation data that are used as regression model input. CAC weather station density is sparse across the U.S. in many major agricultural areas compared to NCDC weather station …

Tests And Estimators Of Multiplicative Models For Variety Trials, P. L. Cornelius, J. Crossa, M. S. Seyedsadr

Conference on Applied Statistics in Agriculture

Some recently obtained results on cross validation, hypothesis test and estimation procedures for multiplicative models applied to multi-site crop variety trials are presented. The PRESS statistic is more sensitive to overfitting and choice of model form than data-splitting cross-validation. Because of their extreme liberality, Gollob F-tests should not be used to test multiplicative terms. FGH tests effectively control Type I error, but are conservative for tests of terms for which the previous term is small. "Simulation tests" have greater power than FGH tests, but still effectively control Type I error rates. Simulation results and cross validation in two examples suggest …

Designing Alfalfa Yield Trials For Comparing Long-Term Yields, G. B. Schaalje, S. N. Acharya

Conference on Applied Statistics in Agriculture

An aspect of experimental design that must be taken into consideration for variety trials of perennial crops is the number of years to continue the trial. By tradition, alfalfa forage yield trials are harvested for three or four production years, but the consumers of information from these trials, the producers, often keep their stands in production for more than four years. This study developed a statistical efficiency measure for evaluating the adequacy of forage trial designs with specified numbers of years and replicates, based on a multivariate linear model. The measure was applied to data from four long-term trials grown …

On Multivariate Analyses Of Crossover Designs, Dallas E. Johnson, Carla Goad

Conference on Applied Statistics in Agriculture

In crossover experiments, treatments are assigned to experimental units in successive periods. Traditional analyses of crossover designs with three or more periods assume that the observations in successive periods satisfy conditions similar to those utilized in the analysis of many repeated measures experiments. The successive measurements are assumed to satisfy conditions known as the Huynh-Feldt conditions. This paper gives a test for the Huynh-Feldt conditions and discusses possible analyses of crossover experiments, including tests for carryover, when the Huynh-Feldt conditions are not satisfied.

The Estimation Of Fixed Effects In A Mixed Linear Model, F. Nabugoomu, O. B. Allen

Conference on Applied Statistics in Agriculture

The estimation of fixed effects is considered for small, unbalanced, mixed linear models. The two-stage estimator, in which the variance components are first estimated by ML or REML, is compared to the intra-block (IB) estimator, the ordinary least squares (OLS) estimator (ignoring the random effects) and the Gauss-Markov (GM) estimator. Comparison is made, based on 100 simulated data sets each, for 6 designs (3 BIBD's and 3 unbalanced designs). In comparing loss of information, relative to the GM lower bound, the two-stage procedures (using either ML or REML) are recommended for all but the smallest and least balanced design. The …

Simple Estimations Of The Variance Components And The Fixed And Random Effects In Mixed, Three-Stage, Hierarchal Models, C. Philip Cox

Conference on Applied Statistics in Agriculture

FRR (Fixed, Random, Random) hierarchal models in which the first-stage" elements are fixed and the second and third-stage elements are random, are used in analyses of comparative experiments and, extensively, in animal breeding contexts where, in the latter, estimates of the second-stage elements and of combinations of them with first-stage elements, are of practical interest. The two procedures, i) empirical BLUP (Best Linear Unbiased Prediction) and ii) a Bayesian approach, used when the ratio of the within-second-stages and the within-third-stages variances is unknown are 'computationally intensive'. When the ratio of the second- to the third-stage variances is large, an alternative …

Mixed Models Combined Analysis Of Independent Grazing Trials, H. A. Fribourg, J. C. Waller, R. W. Thompson, W. L. Sanders

Conference on Applied Statistics in Agriculture

The mixed models procedure (MMP) was used to analyze pooled data sets from 12 independent studies over 13 yr at 9 locations in 7 states to provide combined estimates of daily gains by beef steers grazing tall fescue pastures with different levels of infestation by Acremonium coenophialum, with and without clover. Spring, summer, and combined spring + summer data were analyzed separately. The MMP permitted estimation of the fixed effects of treatments over a broad inference space of future years and different tall fescue pastures over a wide geographic range, detected some relationships not apparent in the individual studies, …