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A recent paper in Sci. Adv. by Miller et al. concludes that GREs do not help predict whether physics grad students will get Ph.D.s. The paper makes numerous elementary statistics errors, including introduction of unnecessary collider-like stratification bias, variance inflation by collinearity and range restriction, omission of needed data (some subsequently provided), a peculiar choice of null hypothesis on subgroups, blurring the distinction between failure to reject a null and accepting a null, and an extraordinary procedure for radically inflating confidence intervals in a figure. Release of results of simpler models, e.g. without unnecessary stratification, would fix some key problems. The paper exhibits exactly the sort of research techniques which we should be teaching students to avoid.
Despite limiting access to applicants from underrepresented racial and ethnic groups, the practice of using hard or soft GRE cut-off scores in physics graduate program admissions is still a popular method for reducing the pool of applicants. The present study considers whether the undergraduate institutions of applicants have any influence on the admissions process by modelling a physics GRE cut-off score with application data from admissions offices of five universities. Two distinct approaches based on inferential and predictive modelling are conducted. While there is some disagreement regarding the relative importance between features, the two approaches largely agree that including institutional information significantly aids the analysis. Both models identify cases where the institutional effects are comparable to factors of known importance such as gender and undergraduate GPA. As the results are stable across many cut-off scores, we advocate against the practice of employing physics GRE cut-off scores in admissions.
The Physics GRE is currently a required element of the graduate admissions process in nearly all U.S. astronomy programs; however, its predictive power and utility as a means of selecting successful applicants has never been examined. We circulated a short questionnaire to 271 people who have held U.S. prize postdoctoral fellowships in astrophysics between 2010-2015, asking them to report their Physics GRE scores (this should not in any way be interpreted as a belief that a prize fellowship is the best or only metric of success in astronomy). The response rate was 64%, and the responding sample is unbiased with respect to the overall gender distribution of prize fellows. The responses reveal that the Physics GRE scores of prize fellows do not adhere to any minimum percentile score and show no statistically significant correlation with the number of first author papers published. As an example, a Physics GRE percentile cutoff of 60% would have eliminated 44% of 2010-2015 U.S. prize postdoctoral fellows, including 60% of the female fellows. From these data, we find no evidence that the Physics GRE can be used as an effective predictor of success either in or beyond graduate school.
The claim in ref.1 [M. Conte et al: Stern-Gerlach Force on a Precessing Magnetic Moment, Proceedings of PAC07 (http://cern.ch/AccelConf/p07/PAPER/THPAS105.pdf)] that the Stern-Gerlach force on a charged particle with a magnetic moment causes a change in longitudinal momentum proportional to gamma-squared when it traverses a specially configured localized electromagnetic field, contradicts the prediction based on the established interaction Lagrangian. It is shown that extending the calculation in ref. 1 to include the entire spin motion eliminates the gamma-squared term and thus the inconsistency.
In their comment, Poole et al. (2009) aim to show it is highly improbable that the observations described in Chepfer and Noel (2009), and described as NAT-like therein, are produced by Nitric Acid Trihydrate (NAT) particles. In this reply, we attempt to show why there is, in our opinion, too little evidence to reject this interpretation right away.
We comment on a recent manuscript by A. P. Serebrov, et al. regarding residual gas charge exchange in the beam neutron lifetime experiment