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1997

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Articles 1 - 30 of 101

Full-Text Articles in Life Sciences

Using Ranks To Perform Exact And Estimated Exact Tests In Designed Experiments, Scott J. Richter, Mark E. Payton Apr 1997

Using Ranks To Perform Exact And Estimated Exact Tests In Designed Experiments, Scott J. Richter, Mark E. Payton

Conference on Applied Statistics in Agriculture

A procedure is studied that uses rank transformed data to perform exact and estimated exact tests which is an alternative to the commonly used F-ratio test procedure. First, a common parametric test statistic is computed using rank transformed data, where two methods of ranking - ranks taken of the original observations, and ranks taken after aligning the observations - are studied. Significance is then determined using either the exact permutation distribution of the statistic or an estimate of this distribution based on a random sample of all possible permutations. Simulation studies compare the performance of this method to both the …

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Testing Variance Components Using The Glm And Mixed Procedures Of Sas®, Ron Mcnew, Andy Mauromoustakos Apr 1997

Testing Variance Components Using The Glm And Mixed Procedures Of Sas®, Ron Mcnew, Andy Mauromoustakos

Conference on Applied Statistics in Agriculture

The test of a variance component in random and mixed normal linear models can be done using the F statistic from the analysis of variance or the Wald statistic which is the ratio of the variance component estimate to its estimated standard error. These are the methods used in the GLM and MIXED procedures of SAS®. We show that these two tests can give different results on the same data. For the one-way random model, the one-sided Wald test on the among group variance component can never be significant at the 0.05 probability level when the number of levels of …

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The Statistical Analysis Of Active Control Equivalence Studies, Armando Garsd, Susana F. Delfino Apr 1997

The Statistical Analysis Of Active Control Equivalence Studies, Armando Garsd, Susana F. Delfino

Conference on Applied Statistics in Agriculture

In experimental work, the notion of equivalence falls short of the idea of equality. Thus, the effects of two treatments, while not identical, may still be regarded as equivalent if their difference is negligible in a certain sense. This simple distinction raises not only technical difficulties, since of necessity it results in special statistical procedures, but also deeper conceptual issues, since one has to ask why two treatments should be equivalent but not equal, more specifically, whether their being merely equivalent has any bearing on the practical questions posed by the data. In this paper we present examples, drawn from …

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The Analysis Of The Two-Period Repeated Measurements Crossover Design With Application To A Forestry Problem, Armando Garsd, Maria C. Fabrizio, Maria V. López Apr 1997

The Analysis Of The Two-Period Repeated Measurements Crossover Design With Application To A Forestry Problem, Armando Garsd, Maria C. Fabrizio, Maria V. López

Conference on Applied Statistics in Agriculture

The two-period repeated measurements crossover design is not often used in agricultural studies. It is, however, an attractive model, involving the confluence of two powerful statistical ideas, treatment crossover and repeated measurements on the same experimental unit. This paper presents one approach for the statistical analysis of such design based on the work of Wallenstein and Fisher (1977). It is shown how the data may be transformed so that it can be analyzed under the framework of a completely randomized repeated measurements design. We formalize the analysis in the context of a forestry experiment conducted on poplar trees (Populus SP.), …

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The Use Of Inverse Theory On An Ill-Posed Environmental Composite Sampling Problem, V. A. Lancaster, S. Keller-Mcnulty Apr 1997

The Use Of Inverse Theory On An Ill-Posed Environmental Composite Sampling Problem, V. A. Lancaster, S. Keller-Mcnulty

Conference on Applied Statistics in Agriculture

As an alternative to retesting, the use of inverse theory techniques is proposed to resolve the lack of information inherent in composite sampling methods. This paper evaluates the feasibility of combining composite sampling with the inverse theory technique of linear regularization on an environmental site characterization investigation. Federal legislation has mandated the cleanup of hazardous waste sites, creating the need to characterize these sites for various chemical constituents. An abundance of samples, high measurement costs, and limited budgets create the appeal of compositing samples. We propose that the number of costly laboratory analyses can be reduced by combining composite sampling …

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Bootstrap Confidence Intervals From Adaptive Sampling Of An Insect Population, Jeffrey S. Pontius, Mary C. Christman Apr 1997

Bootstrap Confidence Intervals From Adaptive Sampling Of An Insect Population, Jeffrey S. Pontius, Mary C. Christman

Conference on Applied Statistics in Agriculture

We construct 90% normal, percentile, and bias-corrected and accelerated confidence intervals using a finite population bootstrapping algorithm based on adaptive sampling in an agroecosystem. We evaluate the interval estimates based on sampling simulations of a spatially arranged population of plots that contain counts of beet webworms and based on an adaptive condition that generates small networks. The sampling distributions of the original sample estimates and of the bootstrap estimates were generally similar and symmetric. The simulation coverages were from 84% to 90% and similar under any of the sample sizes and any of the three confidence interval types. This study …

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Some Experiences With Neural Networks, Lynda L. Ballou, Dallas E. Johnson Apr 1997

Some Experiences With Neural Networks, Lynda L. Ballou, Dallas E. Johnson

Conference on Applied Statistics in Agriculture

This paper gives a brief overview of artificial neural networks which may be used to model data similar to the kind where one usually considers regression models. Many practitioners believe that neural networks perform better than regression models for prediction purposes. Some simulations were performed using three different neural net programs, namely Braincel, Ripley's S+ program, and Nychka's S+ program. These simulations reveal some interesting aspects of neural net programs which should be of interest to anyone considering the use of neural net programs to model continuous data.

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Some Factors Limiting The Use Of Generalized Linear Models In Agricultural Research, Walter W. Stroup Apr 1997

Some Factors Limiting The Use Of Generalized Linear Models In Agricultural Research, Walter W. Stroup

Conference on Applied Statistics in Agriculture

The generalized linear model (GLM) is a "hot" topic in statistics. Numerous research articles on GLM's appear in each edition of all major journals in statistics. GLM's are the subject of substantial numbers of presentations at most statistics conferences. Despite the high level of interest and research activity within the statistics community, GLM's are not widely used, with some exceptions, by biological scientists in the statistical analysis of their research data. Why? Reasons include 1) many statisticians are not comfortable with GLM's, 2) the biological research community is not familiar with GLM's, and 3) there is little in introductory statistics …

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How Good Are Spatial Glm's? A Simulation Study, Roger G. Collins, Walter W. Stroup, Stephen D. Kachman Apr 1997

How Good Are Spatial Glm's? A Simulation Study, Roger G. Collins, Walter W. Stroup, Stephen D. Kachman

Conference on Applied Statistics in Agriculture

An area of increasing interest to agricultural and ecological researchers is the analysis of spatially correlated non-normal data. A generalized linear model(GLM) accounting for spatial covariance was presented by Gotway and Stroup (1997). Their method included approximate inference based on asymptotic distributions. A simulation study was conducted to assess the small sample behavior of their proposed estimates and test statistics. This study suggests that the spatial GLM yields unbiased estimates of treatment means and differences for binomial data, that the spatial GLM improves precision, as measured by MSE, and that the approximate F-statistic is acceptable for hypothesis testing.

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Alternative Analyses Of Crossover Designs With More Than Two Periods, Carla L. Goad, Dallas E. Johnson Apr 1997

Alternative Analyses Of Crossover Designs With More Than Two Periods, Carla L. Goad, Dallas E. Johnson

Conference on Applied Statistics in Agriculture

A crossover experiment is a special form of a repeated measures experiment. An appropriate analysis of a repeated measures experiment depends on the form of the varian-cecovariance matrix of the repeated measures. Certain forms of this matrix yield valid analysis of variance F -tests while other forms invalidate these tests. In a crossover experiment where analysis of variance tests are invalid, two alternative tests of a linear contrast of the parameters are proposed. In addition to these approximate t-tests, three alternative methods for testing for equal treatment effects and equal carryover effects are proposed. A simulation study is conducted to …

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Bioavailability And Cv Component Comparison In A Crossover, Zhiming Wang, Vince A. Uthoff Apr 1997

Bioavailability And Cv Component Comparison In A Crossover, Zhiming Wang, Vince A. Uthoff

Conference on Applied Statistics in Agriculture

Two medication formulations are compared using noncompartmental pharmacokinetic (PK) variables. However, more than the ratio of mean effects is of interest. A difference in formulation coeficients of varication (CV), within- or between-subject, is sought. The experimental design chosen is a 2 sequence crossover design of the form ABBA and BAAB, where A and B are two medication formulations. A mixed linear model is defined that contains random effects for subjects and for subject by formulation interactions. The model has fixed effects for the average formulation effects and period effects. The 2 formulations are assumed to have different error terms. The …

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Equivalence Testing In Agriculture Experiments, Brian J. Fergen Apr 1997

Equivalence Testing In Agriculture Experiments, Brian J. Fergen

Conference on Applied Statistics in Agriculture

Equivalence testing is a relatively new area of research in statistics. It's development has been motivated in large part by the need for statistical methods for determining if generic drugs are bioequivalent to their name brand counterparts. The application of equivalence testing methods to data resulting from experiments and surveys unrelated to drug development, and in particular agriculture-related experiments, is infrequent and possibly non-existent. These methods provide useful alternatives to the analysis methods currently being used. In this paper, an overview of the philosophy of equivalence testing and a review of equivalence testing methods are presented. Additionally, experimental situations for …

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Covariance Adjustment In Studies Involving Observational Factors Or Covariates Influenced By Treatments, O. B. Allen, I. B. Mandell, J. W. Wilton, L. B. Buchanan-Smith Apr 1997

Covariance Adjustment In Studies Involving Observational Factors Or Covariates Influenced By Treatments, O. B. Allen, I. B. Mandell, J. W. Wilton, L. B. Buchanan-Smith

Conference on Applied Statistics in Agriculture

We extend the definition of adjusted treatment means in the analysis of covariance to deal with the case where some of the covariates are influenced by treatments or where some of the factors are observational. In these cases, comparison of treatment means adjusted to a common value of the covariate may be inappropriate. Partially adjusted means are defined and it is shown that special cases include the usual adjusted means (adjusted to a common value for each of the covariates) and unadjusted means. In fact, in a multifactorial experiment, one can, by appropriate choice of adjustment, compare adjusted means for …

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Comparing The Use Of Block And Covariate Information In Analysis Of Variance, James R. Schwenke Apr 1997

Comparing The Use Of Block And Covariate Information In Analysis Of Variance, James R. Schwenke

Conference on Applied Statistics in Agriculture

Of primary concern in the statistical analysis of the results of an experiment is to quantify the mean response to treatment and to accurately quantify the experimentation error variance. The traditional approach to account for nuisance sources of variation or a heterogeneous population is to group or block the population (or sample) into homogeneous groups with respect to a concomitant variable. A blocking term then is included in the statistical analysis. Alternatively, concomitant variables can be used as covariate information in a statistical analysis. A statistical analysis incorporating blocks assumes that the magnitude of difference in treatment response is equal …

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Analysis Of A Midwest Farmer Survey Of Pest Infestation, Susanne Aref Apr 1997

Analysis Of A Midwest Farmer Survey Of Pest Infestation, Susanne Aref

Conference on Applied Statistics in Agriculture

A survey of farmers rating the severity of crop pest infestation in their fields was conducted in the Midwest in 1992. The purpose of the present study was to detennine summary variables of the pest infestation ratings and the effect of region, soil type, and tillage on these summary variables. The pests were in the following six categories: perennial and annual weeds, insects and diseases of com (Zea mays L.) and insects and diseases of soybean (Glycine max (L.) MerritT). Categorical models were used to analyze individual pest ratings. A non-parametric method, the Sheirer-Ray-Hare extension of the Kruskal-Wallis test …

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Empirical Estimates Of Power For Binomial Data With Mixed Models, R. K. Splan, L. D. Van Vleck, H. D. Hafs Apr 1997

Empirical Estimates Of Power For Binomial Data With Mixed Models, R. K. Splan, L. D. Van Vleck, H. D. Hafs

Conference on Applied Statistics in Agriculture

Observations on return to estrus from anestrus postpartum beef cows were used as the basis for a simulation study to develop a method to determine numbers of locations and animals per treatment per location to achieve a specified power of test. Estimates of among location and total variance were obtained by REML from the data set and then used to generate simulated data for the binomial trait. Each combination of several pre-determined factors was replicated 1000 times. Pre-determined factors were number of locations, number of animals per treatment per location, desired detectable difference due to treatment, alpha-probability level and ratio …

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Alternative Procedures For Estimation Of Nonlinear Regression Parameters, William J. Price, Bahman Shafii Apr 1997

Alternative Procedures For Estimation Of Nonlinear Regression Parameters, William J. Price, Bahman Shafii

Conference on Applied Statistics in Agriculture

Biological research data are often represented using nonlinear model specifications that lend themselves to the testing of relevant hypotheses concerning the model parameters. This is typically achieved with classical nonlinear least squares techniques such as Gauss-Newton or Levenberg-Marquardt which allow for both the estimation and inference phases of the analysis. Under some circumstances, however, sensitivity to data or model specifications may lead these methods to fail convergence tests or exhibit nonlinearity in the parameter estimates, which will in turn limit the usefulness of inferential results. In such cases, other estimation methods may present a means of avoiding these problems while …

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Confidence Intervals For Heritability In A Mixed Linear Model, Brent D. Burch, Hari K. Iyer Apr 1997

Confidence Intervals For Heritability In A Mixed Linear Model, Brent D. Burch, Hari K. Iyer

Conference on Applied Statistics in Agriculture

A family of procedures is given to construct confidence intervals for the heritability of a trait in a mixed linear model. The procedures are applicable for constructing confidence intervals for a ratio of variance components in a mixed linear model having two sources of variation. The resulting intervals are evaluated in terms of expected length. The investigator may select the best confidence interval procedure from the family of procedures based on the interval( s) having short expected length. Confidence intervals for loineye data using bulls from a Red Angus seed stock herd will be presented.

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Using Prior Knowledge Of The Intraclass Correlation To Increase The Power Of Tests For Treatment Means, Marjorie E. Bond, James J. Higgins Apr 1997

Using Prior Knowledge Of The Intraclass Correlation To Increase The Power Of Tests For Treatment Means, Marjorie E. Bond, James J. Higgins

Conference on Applied Statistics in Agriculture

It is common in agricultural research to have experimental units that consist of multiple observational units. For instance, treatments may be applied to pens of animals, pens being the experimental units, while weights are measured on individual animals, the observational units. If there are a small number of experimental units, the power of statistical tests for treatment effects can be small regardless of the number of observational units. We show that it is possible to increase the power of such statistical tests by taking advantage of prior knowledge of the intraclass correlation. Our assertion is that such prior knowledge is …

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Analysing Binary Data In A Repeated Measurements Setting Using Sas, Eleanor F. Allan Apr 1997

Analysing Binary Data In A Repeated Measurements Setting Using Sas, Eleanor F. Allan

Conference on Applied Statistics in Agriculture

Whilst the repeated measurements methods appropriate for the analysis of normally distributed data are well established, methods for handling binary and categorical data in a repeated measurements context are not so commonly known or used. The application of population averaged models and subject effects models to repeated binary data are discussed and their implementation with the aid of SAS are illustrated by example. comparisons with other approaches are also considered.

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Editor's Preface, Table Of Contents, And List Of Attendees, George A. Milliken Apr 1997

Editor's Preface, Table Of Contents, And List Of Attendees, George A. Milliken

Conference on Applied Statistics in Agriculture

These proceedings contain papers presented in the ninth annual Kansas State University Conference on Applied Statistics in Agriculture, held in Manhattan, Kansas, April 27-29, 1997.

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Field Research 1997, Dale L. Fjell Jan 1997

Field Research 1997, Dale L. Fjell

Kansas Agricultural Experiment Station Research Reports

No abstract provided.

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High Carbon Dioxide, Modified-Atmosphere Packaging (Map) For Beef Steaks, S.E. Luchsinger, Melvin C. Hunt, Donald H. Kropf Jan 1997

High Carbon Dioxide, Modified-Atmosphere Packaging (Map) For Beef Steaks, S.E. Luchsinger, Melvin C. Hunt, Donald H. Kropf

Kansas Agricultural Experiment Station Research Reports

To determine the effects of storage in a high-carbon dioxide, modified-atmosphere package (MAP) on shelf life, beef strip steaks were packaged under 30% CO2-70% N2 and stored for up to 42 days at 30 or 38 ÌŠF. Aerobic plate counts (APC) and lactic acid bacteria (LAB) counts in these ExtendPak™ packages were well below the threshold of spoilage even after 42 days of MAP storage. After 28 days of storage, steaks stored in vacuum packages had APC counts 1.0 log 10 greater than steaks in MAP. APCs increased during a 5-day display period in steaks store d in vacuum packages, …

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Liquid Smoke Effects On Escherichia Coli O157:H7 In Beef Trimmings And Ground Beef Patties, R. Estrada-Munoz, Elizabeth A.E. Boyle, James L. Marsden Jan 1997

Liquid Smoke Effects On Escherichia Coli O157:H7 In Beef Trimmings And Ground Beef Patties, R. Estrada-Munoz, Elizabeth A.E. Boyle, James L. Marsden

Kansas Agricultural Experiment Station Research Reports

Liquid smoke (LS) reduce d Escherichia coli O157:H7 counts in inoculated beef trimmings and ground beef patties. The counts were reduced (P<.05) by .5 log 10 cfu/g immediately after beef trimmings were treated with 8% LS and by 1.2, 2.0, 1.6, and 2.3 log 10 cfu/g after the trimmings were formed into patties and tested or stored under refrigeration for 1, 2, and 3 days, respectively (2 log10 reduction represents 99%) Thus, LS could make beef-containing products safer with respect to foodborne pathogens.

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Use Of Video Image Analysis, Ribeye Grids, And Linear Ribeye Measurements To Predict And Compare Ribeye Areas From Carcass Left And Right Sides, A.T. Waylan, R.E. Campbell, John A. Unruh Jan 1997

Use Of Video Image Analysis, Ribeye Grids, And Linear Ribeye Measurements To Predict And Compare Ribeye Areas From Carcass Left And Right Sides, A.T. Waylan, R.E. Campbell, John A. Unruh

Kansas Agricultural Experiment Station Research Reports

Ribeye tracings from 265 beef carcasses were used to compare ribeye areas from right and left sides. When video image analysis (VIA) was used to determine ribeye area, no difference (P=.48) was observed between right and left sides. However, when ribeye area was determine d by using USDA grids, those on the left side were slightly larger (P<.01) than those on right side. This difference is negligible considering the wide rang e in variation (SD=.68 in2) between right and left side ribeye areas. Ribeye area correlations between VIA and grid result s were high for both right (.96) and left (.95) sides. Linear measures (length, midwidth, and widest width) of ribeyes predicted ribeye area with reasonable accuracy ( R2=.90 and .91). These methods provide several options to determine ribeye area. However, data collectors need to realize that the difference between right and left side ribeye areas may be a greater variable than the sensitivity of the method used.

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Delineation Of Geographic Markets For Fed Cattle, Ted C. Schroeder Jan 1997

Delineation Of Geographic Markets For Fed Cattle, Ted C. Schroeder

Kansas Agricultural Experiment Station Research Reports

Determining the extent of geographic markets for fed cattle is important for monitoring performance of the industry. The ability of packing plants to influence prices is determined in part by their ability to segment the market for fed cattle and isolate themselves from plants in other regions. This study analyzed transaction data from 43 U.S. steer and heifer slaughter plants collected by the Grain Inspection Packers and Stockyards Program for approximately a 1-year period during 1992-93. Beef packers procured an average of 64% of their cattle within 75 miles of packing plants, 82 % within 150 miles, and 92% within …

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Effect Of Grain Sorghum Particle Size And Digest “M” Enzyme Treatment On Performance Of Growing Steers, T.J. Kessen, D.D. Simms, Gerry L. Kuhl, James S. Drouillard Jan 1997

Effect Of Grain Sorghum Particle Size And Digest “M” Enzyme Treatment On Performance Of Growing Steers, T.J. Kessen, D.D. Simms, Gerry L. Kuhl, James S. Drouillard

Kansas Agricultural Experiment Station Research Reports

A 73-day growing study utilizing 203 crossbred steers (681 lb) and a digestion trial examined the effect o f sorghum grain particle size on rumen fermentation, ration digestibility, and performance of growing steers fed 37% grain and 63% ground alfalfa. Dry-rolled grain sorghum p article sizes in both trials were about 2000, 1500, and 1000 microns, for the coarse- (CR), medium- (MR), and fine-rolled (FR) treatments , respectively. Coarsely rolled corn (2000 microns) was included as a positive control. In the growing study, half of sorghum was treated at feeding time with an enzyme product, Digest "M". The rations were …

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Effect Of Revalor-G On The Performance Of Stocker Heifers Grazing Irrigated, Smooth Bromegrass Pasture For A Full Season, Gerry L. Kuhl, M.D. Reynolds, Robert T. Brandt Jr., Dale A. Blasi Jan 1997

Effect Of Revalor-G On The Performance Of Stocker Heifers Grazing Irrigated, Smooth Bromegrass Pasture For A Full Season, Gerry L. Kuhl, M.D. Reynolds, Robert T. Brandt Jr., Dale A. Blasi

Kansas Agricultural Experiment Station Research Reports

A 150-day field study was conducted to evaluate single vs. reimplant strategies for stocker heifers grazing irrigated smooth bromegrass . Three hundred forty-three previously nonimplanted British crossbred heifers averaging 494 lb were assigned to one of seven treatments: 1) no implant-control (NC), 2) Revalor-G® (REVG), 3) Ralgro® (RAL), 4) Synovex-H® (SYNH), 5) REVG/REVG, 6) RAL/RAL, and 7) SYNH/SYNH. Reimplanting (Treatments 5, 6 , and 7) was done on day 75 of the trial. In the first 75 days, all implants increased (P<.05) average daily gain (ADG) compared to NC. For the last 75 days (days 75 through 150), heifers implanted with REVG, REVG/REVG, RAL/RAL, and SYNH gained faster (P<.05) than NC or those implanted with RAL, and SYNH/SYNH. No significant differences occur red among the latter three treatments. Over the entire trial, there was no advantage to reimplanting heifers with REVG or RAL. SYNH/ SYNH heifers gained less (P<.05) than their single -implanted counterparts.

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Evaluation Of The Effects Of Carbohydrate Source And Level Of Degradable Intake Protein On The Intake And Digestion Of Tallgrass-Prairie Hay By Beef Steers, J.S. Heldt, R.C. Cochran, C.P. Mathis, B.C. Woods, Gerald L. Stokka, K. C. Olson, Evan C. Titgemeyer, Tiruvoor G. Nagaraja Jan 1997

Evaluation Of The Effects Of Carbohydrate Source And Level Of Degradable Intake Protein On The Intake And Digestion Of Tallgrass-Prairie Hay By Beef Steers, J.S. Heldt, R.C. Cochran, C.P. Mathis, B.C. Woods, Gerald L. Stokka, K. C. Olson, Evan C. Titgemeyer, Tiruvoor G. Nagaraja

Kansas Agricultural Experiment Station Research Reports

Thirteen ruminally fistulated steers were used to determine the effect of carbohydrate (CHO) source and degradable intake protein (DIP) on intake and digestion of tallgrass-prairie hay. In general, DIP supplementation had positive effects on intake and digestion, although response varied somewhat with CHO source. Increasing the amount of supplemental CHO generally decreased hay intake, but effects on digestion were dependent on CHO source.

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Estimating The Undegradable Intake Protein Content Of Two Forages By Different Commercial Proteases, I.E.O. Abdelgadir, R.C. Cochran, E.S. Vanzant, Evan C. Titgemeyer Jan 1997

Estimating The Undegradable Intake Protein Content Of Two Forages By Different Commercial Proteases, I.E.O. Abdelgadir, R.C. Cochran, E.S. Vanzant, Evan C. Titgemeyer

Kansas Agricultural Experiment Station Research Reports

We evaluated the potential of several commercially available proteases for use in predicting the undegradable intake protein (UIP) concentrations o f alfalfa and prairie hay. Protease s differed in their estimates o f the rate of forage protein breakdown an d the amounts of different forage protein fractions . At least one protease appeared to yield acceptable predictions of UIP via a short-term, single time-point assay. Assays of this type deserve further consideration for commercial application.

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