Spurious Correlation Due to Scaling

Scaling is common in empirical accounting research. It is often done to mitigate heteroscedasticity or the influence of firm size on parameter estimates. However, Barth and Clinch conclude that common diagnostic tools are ineffective in detecting various scale effects. Using analytic results and Monte Carlo simulations, we show that common forms of scaling, when misapplied, induce substantial spurious correlation via biased parameter estimates. Researchers, when uncertain about the exact functional form of scale effect, are typically better off dealing with both heteroscedasticity and the influence of larger firms using techniques other than scaling.

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Action Thresholds for Summer Fungicide Sprays and Sequential Classification of Apple Scab Incidence

Plant Disease ◽

10.1094/pdis-93-5-0490 ◽

2009 ◽

Vol 93 (5) ◽

pp. 490-498 ◽

Cited By ~ 13

Author(s):

Odile Carisse ◽

Catherine Meloche ◽

Guy Boivin ◽

Tristan Jobin

Keyword(s):

Decision Making ◽

Monte Carlo ◽

Monte Carlo Simulations ◽

Sequential Sampling ◽

Apple Scab ◽

Parameter Estimates ◽

Ratio Test ◽

Sample Number ◽

Action Thresholds

The objectives of this study were to establish scab incidence thresholds at which summer fungicide sprays should be initiated and to develop sequential sampling for classification plans to facilitate decision making. The relationship between proportion of scabbed leaves per shoot and percent scabbed fruits at harvest was established based on data collected in both experimental and commercial orchards. Action threshold at which fungicide spray program should be initiated in order to maintain fruit scab at harvest below 2% was established at 0.006 scabbed leaves per shoot; hence incidence thresholds of 0.005 and 0.01 scabbed leaves per shoot were evaluated. Sequential sampling for classification procedures (SSCP), using the Wald's sequential probability ratio test (SPRT), were developed based on a beta-binomial distribution and using parameter estimates of the binary power law. Monte Carlo simulations were used to establish the probability of classifying mean scab incidence as less than the action thresholds (pth = 0.005 and pth = 0.01). Operating characteristic (OC) and average sample number (ASN) curves were established for eight combinations of stop lines and error levels (α and β). Based on the results of the Monte Carlo simulations, four sets of stop lines (two for each pth threshold) were selected for further evaluation. Bootstrap simulations of 50 data sets indicated that both the OC and ASN curves for each of the four pairs of stop lines were similar to OC and ASN values determined by Monte Carlo simulation. When validated with data not used to construct the models, the SSCPs provided the appropriate classification in 98 and 95% of the simulations for the pth = 0.005 and pth = 0.01 (α = 0.05 and β = 0.10), respectively. The sequential sampling plans developed in this study should allow for rapid and accurate classification of the incidence of apple scab on leaves, and aid in sampling for summer scab management decision making.

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Exponentiation in QED and Quasi-Stable Charged Particles

Symmetry ◽

10.3390/sym11111389 ◽

2019 ◽

Vol 11 (11) ◽

pp. 1389 ◽

Cited By ~ 1

Author(s):

Stanisław Jadach ◽

Wiesław Płaczek ◽

Maciej Skrzypek

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Pair Production ◽

High Precision ◽

Functional Form ◽

Charged Particles ◽

Soft Photon ◽

Photon Radiation ◽

Soft Limit

In this note we present a new exponentiation scheme of soft photon radiation from charged quasi-stable resonances. It generalizes the well established scheme of Yennie, Frautschi and Suura. While keeping the same functional form of an exponent, the new scheme is both exact in its soft limit and accounts properly for the kinematical shift in resonant propagators. We present the scheme on an example of two processes: a toy model of single W production in e ν scattering and the W pair production and decay in e + e − annihilation. The latter process is of relevance for the planned FCCee collider where high precision of Monte Carlo simulations is a primary goal. The proposed scheme is a step in this direction.

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Unreliable Inferences About Unobserved Processes: A Critique of Partial Observability Models

Political Science Research and Methods ◽

10.1017/psrm.2017.3 ◽

2017 ◽

Vol 6 (2) ◽

pp. 381-391

Author(s):

Carlisle Rainey ◽

Robert A. Jackson

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Functional Form ◽

Explanatory Variable ◽

Partial Observability ◽

Large Sample ◽

Sample Bias ◽

Partially Observable

Methodologists and econometricians advocate the partial observability model as a tool that enables researchers to estimate the distinct effects of a single explanatory variable on two partially observable outcome variables. However, we show that when the explanatory variable of interest influences both partially observable outcomes, the partial observability model estimates are extremely sensitive to misspecification. We use Monte Carlo simulations to show that, under partial observability, minor, unavoidable misspecification of the functional form can lead to substantial large-sample bias, even though the same misspecification leads to little or no bias under full observability.

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Use of Monte Carlo Simulations To Select Therapeutic Doses and Provisional Breakpoints of BAL9141

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.5.1713-1718.2004 ◽

2004 ◽

Vol 48 (5) ◽

pp. 1713-1718 ◽

Cited By ~ 56

Author(s):

Johan W. Mouton ◽

Anne Schmitt-Hoffmann ◽

Stuart Shapiro ◽

Norman Nashed ◽

Nieko C. Punt

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Staphylococcus Epidermidis ◽

Parameter Estimates ◽

Dosing Regimen ◽

Target Attainment ◽

Methicillin Resistant ◽

Dose Study ◽

Time Periods ◽

Therapeutic Doses

ABSTRACT BAL9141, a new antimicrobial agent belonging to the class of parenteral pyrrolidinone-3-ylidenemethyl cephalosporins, is active against most gram-positive microorganisms, including methicillin-resistant variants (methicillin-resistant Staphylococcus aureus [MRSA] and methicillin-resistant Staphylococcus epidermidis [MRSE]), as well as against penicillin-resistant pneumococci (PRP) and many gram-negative microorganisms. BAL9141 is administered as the prodrug BAL5788, which is rapidly converted to BAL9141 by plasma esterases. Pharmacokinetic (PK) data obtained in a previous multiple ascending dose study were used to fit a population PK model to using the NPEM2 program, yielding PK parameter estimates and its covariance matrix for BAL9141. These estimates and matrix were used to perform Monte Carlo simulations (MCSs) and obtain unbiased target attainment rates (TARs) for various time periods during which the concentration remains above the MIC (T >MIC). Assuming a T >MIC of 40%, TARs of 100% were reached with a dose of 500 mg/liter every 12 h for pathogens with MICs of 2 mg/liter and with a dose of 750 mg/liter every 12 h for pathogens with MICs of 4 mg/liter. Because MICs are ≤2 mg/liter for most strains of MRSA, MRSE, and PRP (with some strains showing an MIC of 4 mg/liter), a dosing regimen of 750 mg every 12 h is proposed for clinical studies. The corresponding provisional breakpoint is S (susceptible) ≤ 4 mg/liter.

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Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164854 ◽

1996 ◽

Vol 54 ◽

pp. 478-479

Author(s):

Matthew T. Johnson ◽

Ian M. Anderson ◽

Jim Bentley ◽

C. Barry Carter

Keyword(s):

Monte Carlo ◽

Quantitative Analysis ◽

Monte Carlo Simulations ◽

Cross Section ◽

Spatial Resolution ◽

Low Voltage ◽

Magnesium Ferrite ◽

X Ray ◽

Interaction Volume ◽

Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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