20,323 research outputs found
Pseudo-R2 Measures for Some Common Limited Dependent Variable Models
A large number of different Pseudo-R2 measures for some common limited dependent variable models are surveyed. Measures include those based solely on the maximized likelihoods with and without the restriction that slope coefficients are zero, those which require further calculations based on parameter estimates of the coefficients and variances and those that are based solely on whether the qualitative predictions of the model are correct or not. The theme of the survey is that while there is no obvious criterion for choosing which Pseudo-R2 to use, if the estimation is in the context of an underlying latent dependent variable model, a case can be made for basing the choice on the strength of the numerical relationship to the OLS-R2 in the latent dependent variable. As such an OLS-R2 can be known in a Monte Carlo simulation, we summarize Monte Carlo results for some important latent dependent variable models (binary probit, ordinal probit and Tobit) and find that a Pseudo-R2 measure due to McKelvey and Zavoina scores consistently well under our criterion. We also very briefly discuss Pseudo-R2 measures for count data, for duration models and for prediction-realization tables
Translation of Time-Reversal Violation in the Neutral K-Meson System into a Table-Top Mechanical System
Weak interactions break time-reversal (T) symmetry in the two-state system of
neutral K mesons. We present and discuss a two-state mechanical system, a
Foucault-type pendulum on a rotating table, for a full representation of K0
K0bar transitions by the pendulum motions including T violation. The pendulum
moves with two different oscillation frequencies and two different magnetic
dampings. Its equation of motion is identical with the differential equation
for the real part of the CPT-symmetric K-meson wave function. The pendulum is
able to represent microscopic CP and T violation with CPT symmetry owing to the
macroscopic Coriolis force which breaks the symmetry under reversal-of-motion.
Video clips of the pendulum motions are shown as supplementary material.Comment: 11 pages, 5 figures, 1 external url with video clip
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