2,247 research outputs found
Iatrogenic Specification Error: A Cautionary Tale of Cleaning Data
It is common in empirical research to use what appear to be sensible rules of thumb for cleaning data. Measurement error is often the justification for removing (trimming) or recoding (winsorizing) observations whose values lie outside a specified range. This paper considers identification in a linear model when the dependent variable is mismeasured. The results examine the common practice of trimming and winsorizing to address the identification failure. In contrast to the physical and laboratory sciences, measurement error in social science data is likely to be more complex than simply additive white noise. We consider a general measurement error process which nests many processes including the additive white noise process and a contaminated sampling process. Analytic results are only tractable under strong distributional assumptions, but demonstrate that winsorizing and trimming are only solutions for a particular class of measurement error processes. Indeed, trimming and winsorizing may induce or exacerbate bias. We term this source of bias Iatrogenic' (or econometrician induced) error. The identification results for the general error process highlight other approaches which are more robust to distributional assumptions. Monte Carlo simulations demonstrate the fragility of trimming and winsorizing as solutions to measurement error in the dependent variable.
Stress buildup in the Himalaya
The seismic cycle on a major fault involves long periods of elastic strain and stress accumulation, driven by aseismic ductile deformation at depth, ultimately released by sudden fault slip events. Coseismic slip distributions are generally heterogeneous with most of the energy being released in the rupture of asperities. Since, on the long term, the fault's walls generally do not accumulate any significant permanent deformation, interseismic deformation might be heterogeneous, revealing zones of focused stress buildup. The pattern of current deformation along the Himalayan arc, which is known to produce recurring devastating earthquakes, and where several seismic gaps have long been recognized, might accordingly show significant lateral variations, providing a possible explanation for the uneven microseismic activity along the Himalayan arc. By contrast, the geodetic measurements show a rather uniform pattern of interseismic strain, oriented consistently with long-term geological deformation, as indicated from stretching lineation. We show that the geodetic data and seismicity distribution are reconciled from a model in which microseismicity is interpreted as driven by stress buildup increase in the interseismic period. The uneven seismicity pattern is shown to reflect the impact of the topography on the stress field, indicating low deviatoric stresses (<35 MPa) and a low friction (<0.3) on the Main Himalayan Thrust. Arc-normal thrusting along the Himalayan front and east-west extension in southern Tibet are quantitatively reconciled by the model
GDP & Beyond – die europäische Perspektive
Earnings nonresponse in the Current Population Survey is roughly 30% in the monthly surveys and 20% in the annual March survey. Even if nonresponse is random, severe bias attaches to wage equation coefficient estimates on attributes not matched in the earnings imputation hot deck. If nonresponse is ignorable, unbiased estimates can be achieved by omitting imputed earners, yet little is known about whether or not CPS nonresponse is ignorable. Using sample frame measures to identify selection, we find clear-cut evidence among men but limited evidence among women for negative selection into response. Wage equation slope coefficients are affected little by selection but because of intercept shifts, wages for men and to a lesser extent women are understated, as are gender wage gaps. Selection is less severe among household heads/co-heads than among other household members.response bias, imputation, earnings nonresponse, gender gap, CPS
Performance Characterization of a Solenoid-type Gas Valve for the Magnetron Source at FNAL
The magnetron-style ion sources currently in operation at Fermilab
use piezoelectric gas valves to function. This kind of gas valve is sensitive
to small changes in ambient temperature, which affect the stability and
performance of the ion source. This motivates the need to find an alternative
way of feeding H2 gas into the source. A solenoid-type gas valve has been
characterized in a dedicated off-line test stand to assess the feasibility of
its use in the operational ion sources. ion beams have been extracted
at 35 keV using this valve. In this study, the performance of the solenoid gas
valve has been characterized measuring the beam current output of the magnetron
source with respect to the voltage and pulse width of the signal applied to the
gas valve.Comment: 4 pp. arXiv admin note: text overlap with arXiv:1701.0175
Education for Your Health!
The health of the people of Kentucky is of high concern for policymakers and citizens alike. Individuals want to live healthy, productive lives, while policymakers recognize that chronic illnesses cost the state in myriad ways. In this brief, we examine the link between educational attainment and health outcomes. We focus on two groups of health outcomes. The first are behavioral and include choices: tobacco use, alcohol use, obesity, and exercise. The second group are outcomes highly associated with these behaviors: heart attack, angina, stroke, and diabetes. The Center for Disease Control (CDC) estimates that these four diseases may cost Kentuckians over 200 million per year
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Vitis vinifera (Vitales: Vitaceae) as a Reproductive Host of Spissistilus festinus (Hemiptera: Membracidae).
Feeding by the three-cornered alfalfa hopper, Spissistilus festinus (Say) (Hemiptera: Membracidae) results in girdling of grapevine petioles and shoots. Its significance as an economic pest of grape has increased since it was shown to transmit Grapevine red blotch virus (GRBV) in a greenhouse study. However, the status of grapevines as a reproductive host for S. festinus remained undetermined. Adult S. festinus were caged onto three regions of the grapevines: apical shoot, green shoot, and dormant cane. Their ability to reproduce was determined by weekly destructive sampling for 7 wk. Successful oviposition and nymphal emergence were observed on apical and green shoots, but not on dormant canes. However, insect development beyond the second nymphal instar did not occur. Knowledge of S. festinus reproduction on grapevines will be an important consideration in designing management guidelines to minimize the spread of GRBV in vineyards
Education Pays Everywhere!
Economists and other researchers have long demonstrated the relationship between education and earnings. In this brief, we focus on the relationship between educational attainment and earnings in the state of Kentucky. Our results, in many ways, are unsurprising, as the old ad campaign said, “Education Pays.” What may be surprising is that we demonstrate that education pays not only in the big cities of Lexington and Louisville, but also in the more rural parts of the state, such as eastern Kentucky and western Kentucky
Want a Job? Get a College Degree
While it is well known that a positive relationship exists between educational attainment and earnings for those who are in the labor market, an important part of how education impacts the well-being of families in Kentucky is the access to employment that it provides. In this brief, we examine the relationship between education and two measures of employment status: unemployment and labor force participation. What we find is quite striking: not only do those with higher education experience less unemployment, they are far more likely to be participating in the labor market. Education leads to better access to employment
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