127 research outputs found
Nonparametric maximum likelihood approach to multiple change-point problems
In multiple change-point problems, different data segments often follow
different distributions, for which the changes may occur in the mean, scale or
the entire distribution from one segment to another. Without the need to know
the number of change-points in advance, we propose a nonparametric maximum
likelihood approach to detecting multiple change-points. Our method does not
impose any parametric assumption on the underlying distributions of the data
sequence, which is thus suitable for detection of any changes in the
distributions. The number of change-points is determined by the Bayesian
information criterion and the locations of the change-points can be estimated
via the dynamic programming algorithm and the use of the intrinsic order
structure of the likelihood function. Under some mild conditions, we show that
the new method provides consistent estimation with an optimal rate. We also
suggest a prescreening procedure to exclude most of the irrelevant points prior
to the implementation of the nonparametric likelihood method. Simulation
studies show that the proposed method has satisfactory performance of
identifying multiple change-points in terms of estimation accuracy and
computation time.Comment: Published in at http://dx.doi.org/10.1214/14-AOS1210 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Zipper: Addressing degeneracy in algorithm-agnostic inference
The widespread use of black box prediction methods has sparked an increasing
interest in algorithm/model-agnostic approaches for quantifying
goodness-of-fit, with direct ties to specification testing, model selection and
variable importance assessment. A commonly used framework involves defining a
predictiveness criterion, applying a cross-fitting procedure to estimate the
predictiveness, and utilizing the difference in estimated predictiveness
between two models as the test statistic. However, even after standardization,
the test statistic typically fails to converge to a non-degenerate distribution
under the null hypothesis of equal goodness, leading to what is known as the
degeneracy issue. To addresses this degeneracy issue, we present a simple yet
effective device, Zipper. It draws inspiration from the strategy of additional
splitting of testing data, but encourages an overlap between two testing data
splits in predictiveness evaluation. Zipper binds together the two overlapping
splits using a slider parameter that controls the proportion of overlap. Our
proposed test statistic follows an asymptotically normal distribution under the
null hypothesis for any fixed slider value, guaranteeing valid size control
while enhancing power by effective data reuse. Finite-sample experiments
demonstrate that our procedure, with a simple choice of the slider, works well
across a wide range of settings
Selective Conformal Inference with FCR Control
Conformal inference is a popular tool for constructing prediction intervals
(PI). We consider here the scenario of post-selection/selective conformal
inference, that is PIs are reported only for individuals selected from an
unlabeled test data. To account for multiplicity, we develop a general split
conformal framework to construct selective PIs with the false
coverage-statement rate (FCR) control. We first investigate the Benjamini and
Yekutieli (2005)'s FCR-adjusted method in the present setting, and show that it
is able to achieve FCR control but yields uniformly inflated PIs. We then
propose a novel solution to the problem, named as Selective COnditional
conformal Predictions (SCOP), which entails performing selection procedures on
both calibration set and test set and construct marginal conformal PIs on the
selected sets by the aid of conditional empirical distribution obtained by the
calibration set. Under a unified framework and exchangeable assumptions, we
show that the SCOP can exactly control the FCR. More importantly, we provide
non-asymptotic miscoverage bounds for a general class of selection procedures
beyond exchangeablity and discuss the conditions under which the SCOP is able
to control the FCR. As special cases, the SCOP with quantile-based selection or
conformal p-values-based multiple testing procedures enjoys valid coverage
guarantee under mild conditions. Numerical results confirm the effectiveness
and robustness of SCOP in FCR control and show that it achieves more narrowed
PIs over existing methods in many settings
Evaluation of Analgesic and Anti-Inflammatory Activities of Water Extract of Galla Chinensis In Vivo
Aim. Pain and inflammation are associated with many diseases in humans and animals. Galla Chinensis, a traditional Chinese medicine, has a variety of pharmacological properties. The purpose of this study was to evaluate analgesic and anti-inflammatory activities of Galla Chinensis through different animal models. Method. The analgesic activities were evaluated by hot-plate and writhing tests. The anti-inflammatory effects were assessed by ear edema, capillary permeability, and paw edema tests. The contents of cytokines (NO, iNOS, PGE2, and IL-10) in serum of rats in paw edema test were inspected by ELISA assays. Results. In the hot-plate test, Galla Chinensis could significantly extend pain threshold when compared to control group. The inhibitory rates of writhes ranged from 36.62% to 68.57% in Galla Chinensis-treated mice. Treatment with Galla Chinensis (1 and 0.5 g/kg) could significantly inhibit ear edema (47.45 and 36.91%, resp.; P < 0.01). Galla Chinensis (1 g/kg) had significant (P < 0.05) anti-inflammatory activity in capillary permeability test (29.04%). In carrageenan-induced edema test, the inhibitory rates were 43.71% and 44.07% (P < 0.01) at 1 h and 2 h after administration of Galla Chinensis (1 g/kg), respectively, and the levels of proinflammatory cytokines were significantly reduced. Conclusion. These results suggest that Galla Chinensis has analgesic and anti-inflammatory effects, which may be a candidate drug for the treatment of inflammation and pain
In Vivo
Aim. Dermatophytosis is one of the main fungal diseases in humans and animals all over the world. Galla chinensis, a traditional medicine, has various pharmacological effects. The goal of this study was to evaluate the treatment effect of Galla chinensis solution (GCS) on dermatophytosis-infected dogs (Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes, resp.). Methods. The treatment effects of GCS were evaluated by mycological cure rates and clinical score comprised of three indices, including inflammation, hair loss, and lesion scale. Results. The results showed that, in the three models of dermatophytosis, GCS significantly (P<0.05) improved skin lesions and fungal eradication. GCS (10% and 5%) had higher efficacy compared to the positive control (Tujingpi Tincture). The fungal eradication efficacy exceeds 85% after treatment with GCS (10%, 5%, and 2.5%) on day 14. Conclusion. The GCS has antidermatophytosis effect in dogs, which may be a candidate drug for the treatment of dermatophytosis
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