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Articles 1 - 25 of 25
Full-Text Articles in Life Sciences
Modeling And Design To Detect Interaction Of Insecticides, Herbicides And Other Similar Compounds, Timothy E. O'Brien
Modeling And Design To Detect Interaction Of Insecticides, Herbicides And Other Similar Compounds, Timothy E. O'Brien
Conference on Applied Statistics in Agriculture
This paper discusses model and experimental design aspects of agricultural studies aimed at discerning antagonism or synergy between two or more insecticides, herbicides, or other similar compounds. The developed methods involve a broad class of generalised nonlinear models, which are easily fitted to data using popular statistical packages such as the NLMIXED procedure in SAS® software. Sample computer code is given in the Appendix.
Comparing Correlated Parameter Estimates For Nonlinear Pet Model, J. Wu, A. Parkhurst, K. Eskridge, D. Travnicek, T. Brown-Brandi, R. Eigenberg, G. L. Hahn, J. Nienaber, T. Mader, D. Spiers
Comparing Correlated Parameter Estimates For Nonlinear Pet Model, J. Wu, A. Parkhurst, K. Eskridge, D. Travnicek, T. Brown-Brandi, R. Eigenberg, G. L. Hahn, J. Nienaber, T. Mader, D. Spiers
Conference on Applied Statistics in Agriculture
The nonlinear PET model based on Newton's law of cooling can be used to estimate body temperature in cattle, T b challenged by hot cyclic chamber temperatures, T a . The PET model has four biologically meaningful parameters: K, the thermal constant; Δ, the difference between T b and adjusted T a ; Υ the proportion of variation in T b comparable to variation in Ta ; T bini, the initial body temperature. The two parameters Y and Δ are highly correlated in the current version of the model. This study looks at other ways to parameterize …
Statistical Analysis Of The Effects Of Mixing Potato Varieties On Late Blight, Z. Su, K. A. Garrett, L. N. Zuniga, E. Roncal, G. A. Forbes, C. C. Mundt, R. J. Nelson
Statistical Analysis Of The Effects Of Mixing Potato Varieties On Late Blight, Z. Su, K. A. Garrett, L. N. Zuniga, E. Roncal, G. A. Forbes, C. C. Mundt, R. J. Nelson
Conference on Applied Statistics in Agriculture
A field study in two regions of Peru was conducted to determine how host-diversity effects on potato late blight varied geographically. Foliar disease severity was evaluated separately for the potato varieties in mixtures as well as in the single-variety plots. The TAUDPC (truncated area under the disease progress curve) and RMR (relative mixture response) for each site were analyzed separately using SAS mixed effects model procedures. While there was little difference between the sites in the 1997-1998 season, host-diversity effects were generally greater near Huancayo than near Cajamarca in the 1998-1999 season. Estimates of host-diversity effects from studies in Oregon …
Suggestions For Presenting Kriging Results, D. W. Meek, T. J. Sauer
Suggestions For Presenting Kriging Results, D. W. Meek, T. J. Sauer
Conference on Applied Statistics in Agriculture
Kriging maps are often part of the reported analyses in many environmental research studies including those our agency is working on in the area of precision/sustainable farming. All to often important details on the underlying variography and/or kriging procedures are omitted. Likewise the content and form of presenting kriging results vary greatly. Often features of the underlying variability are not readily seen. Instead of reviewing poor practice in current literature, we offer guidelines for reporting the methodology and presenting the results with the use of soil test phosphorus (STP) measures from a real world pasture study. Relevantly, the stationarity assumption …
Threshold Sire Models For Estimating Genetic Parameters For Stayability In Beef Cows, Gonzalo Martinez, S. D. Kachman, L. D. Van Vleck
Threshold Sire Models For Estimating Genetic Parameters For Stayability In Beef Cows, Gonzalo Martinez, S. D. Kachman, L. D. Van Vleck
Conference on Applied Statistics in Agriculture
Stayability is the ability of a beef cow to remain in production to a specified age. In this study, the interest was in determining the genetic relationship between stayability to an early age with stayability to a later age. A nested threshold sire model for stayability was used here to estimate the genetic relationship between stayability to different ages. Genetic correlations were estimated among six different stayability traits using records from 1,868 Hereford cows. The model included period and year of birth as fixed factors and sire as a random factor. The numerator relationship matrix accounted for all known relationships …
Comparing Measuring Methods Using The Sensitivity Ratio: An Application To Resistance Screening In Soybeans, Gabotepele Madisa, Kent M. Eskridge, Kris S. Powers, James R. Steadman, Rebecca Higgins, Connie Bellows
Comparing Measuring Methods Using The Sensitivity Ratio: An Application To Resistance Screening In Soybeans, Gabotepele Madisa, Kent M. Eskridge, Kris S. Powers, James R. Steadman, Rebecca Higgins, Connie Bellows
Conference on Applied Statistics in Agriculture
When there are several methods of measuring a physical or chemical property, it is necessary to determine which method is best. If both methods are measured on the same scale, the most precise method will be preferred. However, often the methods have different scales. The sensitivity ratio allows for explicit comparison of methods with different scales. We use the sensitivity ratio to compare soybean resistance screening methods to evaluate the resistance of soybean varieties to Sclerotinia sclerotiorum. When compared to the root mean square error or the coefficient of variation, the sensitivity ratio can order methods differently both when the …
Simple Step-Stress Testing With Covariate In Agriculture, Larry Cleair, Imad H. Khamis, Mohamad Ai-Haj Ebrahem
Simple Step-Stress Testing With Covariate In Agriculture, Larry Cleair, Imad H. Khamis, Mohamad Ai-Haj Ebrahem
Conference on Applied Statistics in Agriculture
In industry product testing can be an expensive and time-consuming process. Testing design changes in long-lived products could cause lengthy delays in product introduction or improvement. As an alternative, accelerated life testing can quickly yield information on product life by exposing the product to conditions beyond those of normal design stress. To further streamline this process a two step-stress test will take all elements to failure in a relatively short time. Variables within the sample other than the one that we are controlling in the step-stress testing are uncontrolled but observed and are called covariates. A statistical relationship between the …
Hotelling's T2 Approximation For Bivariate Dichotomous Data, Pradeep Singh, Imad Khamis, James Higgins
Hotelling's T2 Approximation For Bivariate Dichotomous Data, Pradeep Singh, Imad Khamis, James Higgins
Conference on Applied Statistics in Agriculture
The comparison of the means of two treatments or populations when more than one variable is measured may be done using Hotelling's T2 statistic. In many real world situations the data obtained are dichotomous, and the assumption of multivariate normality upon which Hotelling's T2 is based is no longer valid. In this paper, an approximate Hotelling T2 test is proposed for bivariate dichotomous data and empirically evaluated in terms of Type I error rate. It is shown that the approximation does a good job of controlling the Type I error rate for a range of bivariate parameters …
Using The Bi-Logistic Model To Estimate Body Temperature In Feedlot Cattle, M. Kerek, A. M. Parkhurst, T. L. Mader
Using The Bi-Logistic Model To Estimate Body Temperature In Feedlot Cattle, M. Kerek, A. M. Parkhurst, T. L. Mader
Conference on Applied Statistics in Agriculture
Processing and handling cattle require an expenditure of energy causing an elevation of body temperature, depending on the ambient conditions. More knowledge of body temperature, Tb, dynamics could lead to more specific recommendations of how far cattle can be moved without stress. The bi-Iogistic model has been used to describe the handling process. This model estimates several important biological parameters: rate of increase in Tb (rate of heat challenge), the maximum Tb (max Tb), time to reach maximum Tb (tmax) and recovery rate (rate of decrease in Tb). The objectives of this study are: to compare parameter estimates from the …
Detection Power Of Random, Case-Control, And Case-Parent Control Designs For Association Tests And Genetic Mapping Of Complex Traits, Guoping Shu, Beiyan Zeng, Oscar Smith
Detection Power Of Random, Case-Control, And Case-Parent Control Designs For Association Tests And Genetic Mapping Of Complex Traits, Guoping Shu, Beiyan Zeng, Oscar Smith
Conference on Applied Statistics in Agriculture
We compared the relative detection power of random, case-control, and case-parent control (TDT) study designs by computer simulation of five parameters: Mode of inheritance (MOl), magnitude of genetic effect (y ), disease susceptibility allele frequency in the founder population ( P I), population age (t ), and the genetic distance (ᶿ ) between disease susceptibility locus ( D), and marker locus (M). Our results show that none of the three study designs can be claimed to be the most powerful (requiring the smallest sample size) constantly under every different genetic context (parameter combination). …
Unreplicated Variety Trials: Effects Of Check Plot Density And Fixed Versus Random Treatments, Tisha Maas, Jeanette Stafford, Boi Sebolai, David Marx, Daryl Travnicek, Jeff Pedersen
Unreplicated Variety Trials: Effects Of Check Plot Density And Fixed Versus Random Treatments, Tisha Maas, Jeanette Stafford, Boi Sebolai, David Marx, Daryl Travnicek, Jeff Pedersen
Conference on Applied Statistics in Agriculture
Crop researchers performing germplasm screenings are often unable to replicate their plots due to scarcity of seed and the large numbers of genotypes being evaluated. The use of known check varieties is a common method of overcoming the difficulties associated with unreplicated trials. In this simulation, we explored the effect of check plot density on the effectiveness of the resulting analysis. We also explored the effect of analyzing treatments as random versus fixed. Our study considers ten different designs with check densities ranging from 5% of the plots to 50%. The designs and analyses were then compared on the basis …
A Bayesian Approach To Assessing Lab Proficency With Qualitative Pcr Assays Used To Detect Biotech Traits In Crop Seed, Kirk M. Remund, Glenn D. Austin
A Bayesian Approach To Assessing Lab Proficency With Qualitative Pcr Assays Used To Detect Biotech Traits In Crop Seed, Kirk M. Remund, Glenn D. Austin
Conference on Applied Statistics in Agriculture
Many seed testing laboratories currently use polymerase chain reaction (PCR) assays to test conventional crop seed for the adventitous presence of biotech trait seed. Seed organizations and companies are spending much time and resources assessing laboratories proficency in running PCR assays. Since many of these assays provide qualitative rather than quantitative results, laboratories must go through a significant effort to obtain adequate assay error estimates. Many sample-processing steps are very similar from assay to assay and therefore error results from different assays may be combined using a Bayesian approach to obtain estimates of assay error rates with increased precision. This …
Variance Testing With Simplicial Data Depth, Karen J. Mcgaughey, George A. Milliken
Variance Testing With Simplicial Data Depth, Karen J. Mcgaughey, George A. Milliken
Conference on Applied Statistics in Agriculture
A method is developed and studied for testing equality of variances based on simplicial data depth and Mood's nonparametric test in the case of two samples. A method for calculating univariate simplicial data depth using a rank transformation is introduced. Type I error rates and power curves are compared for three existing tests for equality of variances and the data depth test using data simulated from the nonnal distribution and 5 nonnormal distributions. In addition, a new method of aligning two samples with unequal location parameters is proposed. This method shows significant improvement over aligning by either the median or …
Cubic Splines For Estimating Lactation Curves And Genetic Parameters Of First Lactation Holstein Cows Treated With Bovine Somatotropin, Bruce J. Degroot, Jeffrey F. Keown, Stephen D. Kachman, Dale Van Vleck
Cubic Splines For Estimating Lactation Curves And Genetic Parameters Of First Lactation Holstein Cows Treated With Bovine Somatotropin, Bruce J. Degroot, Jeffrey F. Keown, Stephen D. Kachman, Dale Van Vleck
Conference on Applied Statistics in Agriculture
The objective was to estimate genetic parameters and fit lactation curves for cows treated or not treated with bovine somatotropin (bST) and fit specific lactation curves for each animal for both random genetic and permanent environmental components from individual test-day milk, fat, and protein yields with a cubic spline model. A total of 70,752 test-day observations for first lactation Holstein cows recorded as treated bST and 73,387 test-day observations for untreated cows that calved between 1994 and early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Carolina. The model included herd test-day, age at first calving, bST …
The Probability Of Preponderancy: An Alternative To The Intraclass Correlation, Ian R. Harris, Brent D. Burch
The Probability Of Preponderancy: An Alternative To The Intraclass Correlation, Ian R. Harris, Brent D. Burch
Conference on Applied Statistics in Agriculture
We propose a new parameter for measuring the influence of a random effect in a mixed linear model. This is the probability of preponderance of the random effect under study over the other random effects. In a one-way random effects model, this is simply the probability the group random effect is larger in absolute size than the individual random effect (or error). We discuss the meaning of the parameter and relate it to the more familiar intraclass correlation coefficient. The new parameter has the appealing property that it is applicable for any distribution, whereas the intraclass correlation has its origins …
A Simulation Study Of Exponential Semiv Arlo Gram Estimation, Edward E. Gbur, Bruce A. Craig, Hao Zhang
A Simulation Study Of Exponential Semiv Arlo Gram Estimation, Edward E. Gbur, Bruce A. Craig, Hao Zhang
Conference on Applied Statistics in Agriculture
Incorporating the spatial structure of data from agricultural field experiments into inference procedures has become an important topic in recent years. As part of a larger project to determine whether or not reliable predictions and estimates can be obtained for sample sizes often encountered in traditional field experimentation, this paper focuses on the small sample estimation of the parameters of the exponential semivariogram model. Simulation studies were conducted for both expanding and fixed domains. The results indicate large sample to sample variation in sample and fitted semivariograms, neither of which may be "close" to the true model. Distributions of individual …
Effect Of Genetic Potential And Feed On Growth Of Young Bulls For Future Breeding, Benjamin G. Mullinix, Walter E. Neville, Jerry F. Baker
Effect Of Genetic Potential And Feed On Growth Of Young Bulls For Future Breeding, Benjamin G. Mullinix, Walter E. Neville, Jerry F. Baker
Conference on Applied Statistics in Agriculture
Over a five-year period (1985-1989), a total of 239 bull calves (Angus=119, Hereford=120) were weaned and placed on summer pasture or fed grain concentrate in a feedlot for purpose of studying growth rate of body weight, hip height, and scrotal circumference over 189 days. Average daily gain [ADG, (final wt - weaning wt) / days in period] has been the standard measure of gwwth. However, this does not address how well a particular bull might have performed. ADG values were ranked at each measurement period (0, 21,49,77, 105, 133,161 and 189 days after weaning), changes in rank were determined for …
Comparing Estimation Procedures For Dose-Response Functions, William J. Price, Bahman Shafii, Ken B. Newman, Shane Early, Joseph P. Mccaffrey, Matthew, J. Morra
Comparing Estimation Procedures For Dose-Response Functions, William J. Price, Bahman Shafii, Ken B. Newman, Shane Early, Joseph P. Mccaffrey, Matthew, J. Morra
Conference on Applied Statistics in Agriculture
The dose-response design is often used in agricultural research when it is necessary to measure a biological response at various levels of an experimental factor. This type of problem is common in chemical and pesticide research, however, it can also occur in other disciplines such as plant, animal, soil, and environmental sciences. While the analysis of dose-response data usually involves fitting a regression curve, the primary objective often centers on the estimation of dose related percentiles such as the LD50 or LC50. These measures are useful for comparing the relative efficacy of various treatments, however, the estimation of the specified …
Quadratic Model To Estimate The Doses Causing The Highest Cholesterol Concentration And The Same Cholesterol Concentration As Control Group, Wuyan Zhang, Steve Nissen, Donald Beitz, Philip Dixon
Quadratic Model To Estimate The Doses Causing The Highest Cholesterol Concentration And The Same Cholesterol Concentration As Control Group, Wuyan Zhang, Steve Nissen, Donald Beitz, Philip Dixon
Conference on Applied Statistics in Agriculture
High plasma cholesterol (particularly high LDL-cholesterol) is a high risk factor for coronary heart disease (CHD), which causes a high CHD morbidity and mortality. Besides clinical drugs, more and more interest is focused on finding natural components in the diet that may have hypocholesterolemic effects. Plant sterols are natural components in human diets and found to have cholesterol-lowering effects in humans. Sheanut oil has a relatively high amolmt of plant sterols. Therefore, the two experiments were designed to investigate the hypocholesterolemic effect of sheanut oil in hamsters. The response was not monotonic. Low doses increased plasma cholesterol, but high doses …
Interval Mapping For Autopolyploids, Dachuang Cao, Bruce A. Craig, R. W. Doerge
Interval Mapping For Autopolyploids, Dachuang Cao, Bruce A. Craig, R. W. Doerge
Conference on Applied Statistics in Agriculture
While extensive progress has been made in quantitative trait locus (QTL) mapping of diploid species, the progress of QTL mapping in polyploids has been limited due to the polyploid's complex genetic architecture. To date, QTL mapping in polyploids has focused primarily on tetraploids with dominant markers and/or codominant markers. In this paper, we extend the interval mapping methodology to any autopolyploid of even ploidy level. Our approach selects a set of likely parental chromosomal configurations (models) using a Bayesian model reduction step. The EM algorithm is then employed to estimate each model's parameters including QTL location, marker dosages, QTL dosages, …
Clustering Environments Based On Crossover Interactions And Using Graphical Approaches To Visualize Clusters, Ken Russell, Kent Eskridge, Daryl Travnicek
Clustering Environments Based On Crossover Interactions And Using Graphical Approaches To Visualize Clusters, Ken Russell, Kent Eskridge, Daryl Travnicek
Conference on Applied Statistics in Agriculture
Crossover interactions occur in evaluation trails when ranks of cultivars change across environments. Determining groups of environments within which crossover interactions are minimized may facilitate making cultivar recommendations. Model-based approaches to finding such clusters have been previously described. Our goal was to describe a new, non-model based approach of defining these clusters and then apply this method to a 59 environment x eight maize (Zea mays L.) cultivar data set. Hierarchical clustering of a 59 x 59 distance matrix defined two environmental clusters within which the total crossover interaction was reduced by approximately one-third and four clusters within …
New Tools For New Times, Terry C. Nelsen, Debra E. Palmquist
New Tools For New Times, Terry C. Nelsen, Debra E. Palmquist
Conference on Applied Statistics in Agriculture
The purpose of this presentation is to challenge statisticians to develop new tools needed by modern scientists. We are in the midst of a Scientific Revolution being driven by computers and the internet. Scientists are gathering huge amounts of data on the usual measurements while continually developing new instruments for new measurements. Data sets full of measurements which may pertain to the scientist's research are easily available on the internet. Scientists are being overwhelmed with data. Agricultural producers and consumers are asking for more information. Scientists need new tools to evaluate variation. They need help with sampling - numbers of …
Small Sample Power Characteristics Of Generalized Mixed Model Procedures For Binary Repeated Measures Data Using Sas, Matthew Beckman, Walter W. Stroup
Small Sample Power Characteristics Of Generalized Mixed Model Procedures For Binary Repeated Measures Data Using Sas, Matthew Beckman, Walter W. Stroup
Conference on Applied Statistics in Agriculture
Researchers in the agricultural and biological sciences often conduct experiments with repeated measures and categorical response variables. Recent advances in statisticalcomputing have made several options available to analyze data from these experiments. For example, SAS has several procedures based on generalized mixed model theory. These include PROC GENMOD, MIXED, NLMIXED, and the GLIMMIX macro. Inference for these procedures depends on asymptotic theory. While statistics literature contains some information about the small-sample behavior, there is much that remains unknown. This presentation will focus on Bernoulli response variables. Power characteristics are compared via simulation for several scenarios involving relatively small repeated measures …
Data Structure With Respect To The Main Effects Model: A Discussion Motivated By A Meta-Analysis Data Set, Dawn M. Vanleeuwen, David S. Birkes, Cynda Clary, Chadelle Robinson
Data Structure With Respect To The Main Effects Model: A Discussion Motivated By A Meta-Analysis Data Set, Dawn M. Vanleeuwen, David S. Birkes, Cynda Clary, Chadelle Robinson
Conference on Applied Statistics in Agriculture
A discussion on data structure relative to the main effects model is motivated by a severely unbalanced meta-analysis data set. This data set is used to highlight the difficulty of assessing data structure when multiple factor data sets are severely unbalanced. Both theoretical results and numerical examples are used to establish that simple approaches to examining data structure using two-way tables provide easily assimilated information about the effect of data unbalance on main effect contrast variances. In addition, notions of balance, proportionality, unbalance, and missing cells with respect to the main effects model are defined in terms of the two-way …
Editor's Preface, Table Of Contents, And List Of Attendees, George A. Milliken
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 fifteenth annual annual Kansas State University Conference on Applied Statistics in Agriculture, held in Manhattan, Kansas, April 27-29, 2003.