9,990 research outputs found
Why can’t measurements based on mathematical models be more user-friendly? problems, causes and suggestions
P values, confidence intervals, or confidence levels for hypotheses?
Null hypothesis significance tests and p values are widely used despite very
strong arguments against their use in many contexts. Confidence intervals are
often recommended as an alternative, but these do not achieve the objective of
assessing the credibility of a hypothesis, and the distinction between
confidence and probability is an unnecessary confusion. This paper proposes a
more straightforward (probabilistic) definition of confidence, and suggests how
the idea can be applied to whatever hypotheses are of interest to researchers.
The relative merits of the different approaches are discussed using a series of
illustrative examples: usually confidence based approaches seem more
transparent and useful, but there are some contexts in which p values may be
appropriate. I also suggest some methods for converting results from one format
to another. (The attractiveness of the idea of confidence is demonstrated by
the widespread persistence of the completely incorrect idea that p=5% is
equivalent to 95% confidence in the alternative hypothesis. In this paper I
show how p values can be used to derive meaningful confidence statements, and
the assumptions underlying the derivation.) Key words: Confidence interval,
Confidence level, Hypothesis testing, Null hypothesis significance tests, P
value, User friendliness.Comment: The essential argument is unchanged from previous versions, but the
paper has been largely rewritten, the argument extended, and more examples
and background context included. 21 pages, 3 diagrams, 3 table
Effects of moderate abundance changes on the atmospheric structure and colours of Mira variables (Research Note)
Aims. We study the effects of moderate deviations from solar abundances upon
the atmospheric structure and colours of typical Mira variables. Methods. We
present two model series of dynamical opacity-sampling models of Mira variables
which have (1) 1 solar metallicity 3 and (2) "mild" S-type C/O abundance ratio
([C/O]=0.9) with typical Zr enhancement (solar +1.0). These series are compared
to a previously studied solar-abundance series which has similar fundamental
parameters (mass, luminosity, period, radius) that are close to those of o Cet.
Results. Both series show noticeable effects of abundance upon stratifications
and infrared colours but cycle-to-cycle differences mask these effects at most
pulsation phases, with the exception of a narrow-water-filter colour near
minimum phase.Comment: 4 pages, 3 figures, accepted for A&
On the general position subset selection problem
Let be the maximum integer such that every set of points in
the plane with at most collinear contains a subset of points
with no three collinear. First we prove that if then
. Second we prove that if
then , which implies all previously known lower bounds on and
improves them when is not fixed. A more general problem is to consider
subsets with at most collinear points in a point set with at most
collinear. We also prove analogous results in this setting
Inference in Hidden Markov Models with Explicit State Duration Distributions
In this letter we borrow from the inference techniques developed for
unbounded state-cardinality (nonparametric) variants of the HMM and use them to
develop a tuning-parameter free, black-box inference procedure for
Explicit-state-duration hidden Markov models (EDHMM). EDHMMs are HMMs that have
latent states consisting of both discrete state-indicator and discrete
state-duration random variables. In contrast to the implicit geometric state
duration distribution possessed by the standard HMM, EDHMMs allow the direct
parameterisation and estimation of per-state duration distributions. As most
duration distributions are defined over the positive integers, truncation or
other approximations are usually required to perform EDHMM inference
Alaska Native Technical Assistance and Resource Center: Final Report
Too often, federal and state justice programs directed at rural, predominately Alaska Native villages do not sufficiently coordinate planning and funding, and are not tailored to fit local cultures and needs. The language and institutional contexts of granting agencies and requests for proposals for grants frame justice problems and their solutions in ways that may or may not relate to the experiences of Alaska Native villages. The Alaska Native Technical Resource Center (ANTARC) was designed as a three-year project to improve village capacity to identify problems and educate the university and granting agencies about the nature of their justice problems and the resources needed to implement solutions. The initial group involved the Justice Center and four rural communities — Gulkana, Kotlik, Wainwright, and Yakutat — with representatives from the communities chosen by village leaders. This report examines ANTARC's evolution, considers its implementation, evaluates the results, and presents recommendations for promoting effective change in Alaska Native villages.Bureau of Justice Assistance, United States Department of Justice Award No. 1999-LB-VX-002Introduction / The Evolution of Antarc / Structure of the Project / Implementation / Evaluating Results / Concluding Recommendations / References / Appendix 1: Proceedings of the March 1999 Antarc Workshop / Appendix 2: Proceedings of the November 1999 Antarc Workshop / Appendix 3: Capra Training Materials / Appendix 4: Evaluation Training Workshop Material
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