765,391 research outputs found
Unexpected abnormal coagulation test results in a 2-year-old child: A case report
Rejection of the sample with repeated blood withdrawal is always an unwanted consequence of sample nonconformity and preanalytical errors,
especially in the most vulnerable population – children. Here is presented a case with unexpected abnormal coagulation test results in a 2-yearold
child with no previously documented coagulation disorder. Child is planned for tympanostomy tubes removal under the anaesthesia driven
procedure, and preoperative coagulation tests revealed prolonged prothrombin time, activated partial thromboplastin time and thrombin time,
with fibrinogen and antithrombin within reference intervals. From the anamnestic and clinical data, congenital coagulation disorder was excluded,
and with further investigation, sample mismatch, clot presence and accidental ingestion of oral anticoagulant, heparin contamination or vitamin K
deficiency were excluded too. Due to suspected EDTA carryover during blood sampling another sample was taken the same day and all tests were
performed again. The results for all tests were within reference intervals confirming EDTA effect on falsely prolongation of the coagulation times in
the first sample. This case can serve as alert to avoid unnecessary loss in terms of blood withdrawal repetitions and discomfort of the patients and
their relatives, tests repeating, prolonging medical procedures, and probably delaying diagnosis or proper medical treatment. It is the responsibility
of the laboratory specialists to continuously educate laboratory staff and other phlebotomists on the correct blood collection as well as on its importance
for the patient’s safety
Simultaneous critical values for -tests in very high dimensions
This article considers the problem of multiple hypothesis testing using
-tests. The observed data are assumed to be independently generated
conditional on an underlying and unknown two-state hidden model. We propose an
asymptotically valid data-driven procedure to find critical values for
rejection regions controlling the -familywise error rate (-FWER), false
discovery rate (FDR) and the tail probability of false discovery proportion
(FDTP) by using one-sample and two-sample -statistics. We only require a
finite fourth moment plus some very general conditions on the mean and variance
of the population by virtue of the moderate deviations properties of
-statistics. A new consistent estimator for the proportion of alternative
hypotheses is developed. Simulation studies support our theoretical results and
demonstrate that the power of a multiple testing procedure can be substantially
improved by using critical values directly, as opposed to the conventional
-value approach. Our method is applied in an analysis of the microarray data
from a leukemia cancer study that involves testing a large number of hypotheses
simultaneously.Comment: Published in at http://dx.doi.org/10.3150/10-BEJ272 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Data driven rank tests for classes of tail alternatives
Tail alternatives describe the frequent occurrence of a non-constant shift in the two-sample problem with a shift function increasing in the tail. The classes of shift functions can be built up using Legendre polynomials. It is important to rightly choose the number of polynomials involved. Here this choice is based on the data, using a modification of Schwarz's selection rule. Given the data driven choice of the model, appropriate rank tests are applied. Simulations show that the new data driven rank tests work very well. While other tests for detecting shift alternatives as Wilcoxon's test may completely break down for important classes of tail alternatives, the new tests have high and stable power. The new tests have also higher power than data driven rank tests for the unconstrained two-sample problem. Theoretical support is obtained by proving consistency of the new tests against very large classes of alternatives, including all common tail alternatives. A simple but accurate approximation of the null distribution makes application of the new tests easy
The penalty in data driven Neyman's tests
Data driven Neyman's tests are based on two elements: Neyman's smooth tests in finite dimensional submodels and a selection rule to choose the "right'' submodel. As selection rule usually (a modification of) Schwarz's rule is applied. In this paper we consider data driven Neyman's tests with selection rules allowing also other penalties than the one in Schwarz's rule. It is shown that the nice properties of consistency against very large classes of alternatives and the more deep result of asymptotic optimality in the sense of vanishing shortcoming continue to hold for other penalties as well, including the one corresponding to Akaike's selection rule
Data-driven rate-optimal specification testing in regression models
We propose new data-driven smooth tests for a parametric regression function.
The smoothing parameter is selected through a new criterion that favors a large
smoothing parameter under the null hypothesis. The resulting test is adaptive
rate-optimal and consistent against Pitman local alternatives approaching the
parametric model at a rate arbitrarily close to 1/\sqrtn. Asymptotic critical
values come from the standard normal distribution and the bootstrap can be used
in small samples. A general formalization allows one to consider a large class
of linear smoothing methods, which can be tailored for detection of additive
alternatives.Comment: Published at http://dx.doi.org/10.1214/009053604000001200 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
The penalty in data driven Neyman's tests
Data driven Neyman's tests are based on two elements: Neyman's smooth tests in finite dimensional submodels and a selection rule to choose the ``right'' submodel. As selection rule usually (a modification of) Schwarz's rule is applied. In this paper we consider data driven Neyman's tests with selection rules allowing also other penalties than the one in Schwarz's rule. It is shown that the nice properties of consistency against very large classes of alternatives and the more deep result of asymptotic optimality in the sense of vanishing shortcoming continue to hold for other penalties as well, including the one corresponding to Akaike's selection rule
Risk management for traffic safety control
This paper offers a range of modelling ideas and techniques from mathematical statistics appropriate for analysing traffic accident data for the East region operation of CLP Power Hong Kong Limited and for the Hong Kong population in general. We further make proposals for alternative ways to record and collect data, and discuss ways to identify the major contributing factors behind accidents. We hope that our findings will enable the design of effective accident prevention strategies for CLP
- …