The Composition Of Normative Groups And Diagnostic Decision Making: Shooting Ourselves In The Foot

Purpose: The normative group of a norm-referenced test is intended to provide a basis for interpreting test scores. However, the composition of the normative group may facilitate or impede different types of diagnostic interpretations. This article considers who should be included in a normative sample and how-this decision must be made relative to the purpose for which a test is intended. Method: The way in which the composition of the normative sample affects classification accuracy is demonstrated through a test review followed by a simulation study. The test review examined the descriptions of the normative group in a sample of 32 child language tests. The mean performance reported in the test manual for the sample of language impaired children was compared with the sample's norms, which either included or excluded children with language impairment. For the simulation, 2 contrasting normative procedures were modeled. The first procedure included a mixed group of representative cases (language impaired and normal cases). The second procedure excluded the language impaired cases from the norm. Results: Both the data obtained from test manuals and the data simulation based on population characteristics supported our claim that use of mixed normative groups decreases the ability to accurately identify language impairment. Tests that used mixed norms had smaller differences between the normative and language impaired groups in comparison with tests that excluded children with impairment within the normative sample. The simulation demonstrated mixed norms that lowered the group mean and increased the standard deviation, resulting in decreased classification accuracy. Conclusions: When the purpose of testing is to identify children with impaired language skills, including children with language impairment in the normative sample can reduce identification accuracy.Communication Sciences and Disorder

Nonlinear dynamics of mode-locking optical fiber ring lasers

We consider a model of a mode-locked fiber ring laser for which the evolution of a propagating pulse in a birefringent optical fiber is periodically perturbed by rotation of the polarization state owing to the presence of a passive polarizer. The stable modes of operation of this laser that correspond to pulse trains with uniform amplitudes are fully classified. Four parameters, i.e., polarization, phase, amplitude, and chirp, are essential for an understanding of the resultant pulse-train uniformity. A reduced set of four coupled nonlinear differential equations that describe the leading-order pulse dynamics is found by use of the variational nature of the governing equations. Pulse-train uniformity is achieved in three parameter regimes in which the amplitude and the chirp decouple from the polarization and the phase. Alignment of the polarizer either near the slow or the fast axis of the fiber is sufficient to establish this stable mode locking

Examination of Factors Influencing Crop Insurance Purchase Decisions of Illinois Farmers

Farm Management, Risk and Uncertainty,

Crop Insurance Purchase Decisions: A Study of Northern Illinois Farmers

When selecting crop insurance coverage, farmers must consider multiple factors. The importance associated with factors that are considered when making crop insurance decisions varies among individual farmers. As available crop insurance options increase, selecting the appropriate coverage becomes a more complicated process. The prevalence of crop insurance participation and the existence of multiple selection criteria also makes understanding participant decisions more difficult. This paper provides findings of a mail survey conducted among farmers in northern Illinois. Mainly, this paper examines factors influencing farmers’ crop insurance purchase decisions, types of coverage purchased, and farmers’ risk attitudes.Crop Production/Industries,

Ethanol Marketing and Input Procurement Practices of U.S. Ethanol Producers: 2008 Survey Results

A mail survey was used to collect information about input procurement and ethanol and co-product marketing practices from 60 U.S. ethanol production facilities. Data were used to answer questions about the conduct or behavior of ethanol producers. It was anticipated that firm conduct or behavior would be fairly homogeneous because the ethanol industry was in Stage II of the industry life-cycle, and societal support for ethanol production resulted in large volumes of publicly available information about technology and markets. Age of facility, size of facility, and type of ownership jointly explained a limited number of differences in responses across ethanol facilities, thus supporting the concept of fairly homogeneous conduct or behavior.entry timing, ethanol, farmer-owned cooperatives, industry life-cycle, Agribusiness, Resource /Energy Economics and Policy, Q11, Q42,

Risk Management Strategies of Illinois Farmers

Farm Management, Risk and Uncertainty,

Middle School Students’ Understanding of Calories, Energy Expenditure and the Nutrition Facts Panel

TORC Abstrac

Dimension reduction for systems with slow relaxation

We develop reduced, stochastic models for high dimensional, dissipative dynamical systems that relax very slowly to equilibrium and can encode long term memory. We present a variety of empirical and first principles approaches for model reduction, and build a mathematical framework for analyzing the reduced models. We introduce the notions of universal and asymptotic filters to characterize `optimal' model reductions for sloppy linear models. We illustrate our methods by applying them to the practically important problem of modeling evaporation in oil spills.Comment: 48 Pages, 13 figures. Paper dedicated to the memory of Leo Kadanof