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Narayanaswamy Balakrishnan - One of the best experts on this subject based on the ideXlab platform.

  • Some Pitman closeness properties pertinent to symmetric Populations
    Statistics, 2013
    Co-Authors: Mohammad Jafari Jozani, Narayanaswamy Balakrishnan, Katherine F. Davies
    Abstract:

    In this paper, we focus on Pitman closeness probabilities when the estimators are symmetrically distributed about the unknown parameter θ. We first consider two symmetric estimators θˆ1 and θˆ2 and obtain necessary and sufficient conditions for θˆ1 to be Pitman closer to the common Median θ than θˆ2. We then establish some properties in the context of estimation under the Pitman closeness criterion. We define Pitman closeness probability which measures the frequency with which an individual order statistic is Pitman closer to θ than some symmetric estimator. We show that, for symmetric Populations, the sample Median is Pitman closer to the Population Median than any other independent and symmetrically distributed estimator of θ. Finally, we discuss the use of Pitman closeness probabilities in the determination of an optimal ranked set sampling scheme (denoted by RSS) for the estimation of the Population Median when the underlying distribution is symmetric. We show that the best RSS scheme from symmetric p...

  • Some Pitman Closeness Properties Pertinent to Symmetric Populations
    arXiv: Statistics Theory, 2012
    Co-Authors: Mohammad Jafari Jozani, Narayanaswamy Balakrishnan, Katherine F. Davies
    Abstract:

    In this paper, we focus on Pitman closeness probabilities when the estimators are symmetrically distributed about the unknown parameter $\theta$. We first consider two symmetric estimators $\hat{\theta}_1$ and $\hat{\theta}_2$ and obtain necessary and sufficient conditions for $\hat{\theta}_1$ to be Pitman closer to the common Median $\theta$ than $\hat{\theta}_2$. We then establish some properties in the context of estimation under Pitman closeness criterion. We define a Pitman closeness probability which measures the frequency with which an individual order statistic is Pitman closer to $\theta$ than some symmetric estimator. We show that, for symmetric Populations, the sample Median is Pitman closer to the Population Median than any other symmetrically distributed estimator of $\theta$. Finally, we discuss the use of Pitman closeness probabilities in the determination of an optimal ranked set sampling scheme (denoted by RSS) for the estimation of the Population Median when the underlying distribution is symmetric. We show that the best RSS scheme from symmetric Populations in the sense of Pitman closeness is the Median and randomized Median RSS for the cases of odd and even sample sizes, respectively.

  • Pitman closeness results concerning ranked set sampling
    Statistics & Probability Letters, 2012
    Co-Authors: Mohammad Jafari Jozani, Katherine F. Davies, Narayanaswamy Balakrishnan
    Abstract:

    We first compare the ranked set sampling (RSS) and simple random sampling schemes for the estimation of the Population Median through Pitman’s measure of closeness. Then, by using Banks’ criterion, we determine the frequency with which an individual order statistic is closer to the Median than some symmetric estimator in an ϵ-neighbourhood of the Median. Finally, we consider the simultaneous Pitman closeness criterion and identify the Median RSS as the optimal RSS scheme for estimating the Population Median.

  • On Pitman's measure of closeness of k-records
    Journal of Statistical Computation and Simulation, 2011
    Co-Authors: Jafar Ahmadi, Narayanaswamy Balakrishnan
    Abstract:

    Pitman closeness of both the upper and lower k-record statistics to the Population quantiles of a location–scale family of distributions is studied. For the Population Median, the Pitman-closest k-record is also determined. In the case of symmetric distributions, the Pitman closeness probabilities of k-record statistics are shown to be distribution-free, and explicit expressions are also derived for these probabilities. Exact expressions are derived for the required probabilities for uniform and exponential distributions. Numerical results are given for these families and also the Pitman-closest k-record is determined.

  • Exact likelihood inference for Laplace distribution based on Type-II censored samples
    Journal of Statistical Planning and Inference, 2011
    Co-Authors: George Iliopoulos, Narayanaswamy Balakrishnan
    Abstract:

    Abstract We develop exact inference for the location and scale parameters of the Laplace (double exponential) distribution based on their maximum likelihood estimators from a Type-II censored sample. Based on some pivotal quantities, exact confidence intervals and tests of hypotheses are constructed. Upon conditioning first on the number of observations that are below the Population Median, exact distributions of the pivotal quantities are expressed as mixtures of linear combinations and of ratios of linear combinations of standard exponential random variables, which facilitates the computation of quantiles of these pivotal quantities. Tables of quantiles are presented for the complete sample case.

Mark W Roberts - One of the best experts on this subject based on the ideXlab platform.

  • altered mercaptopurine metabolism toxic effects and dosage requirement in a thiopurine methyltransferase deficient child with acute lymphocytic leukemia
    The Journal of Pediatrics, 1991
    Co-Authors: Mark W Roberts, Michelle Horner, D K Kalwinsky, William E Evans
    Abstract:

    Thiopurine methyltransferase deficiency, inherited as an autosomal codominant trait, is associated with aberrant mercaptopurine metabolism leading to excessive cellular accumulation of 6-thioguanine nucleotides, the active metabolites of mercaptopurine. We describe a case of severe thiopurine methyltransferase deficiency (activity 8 erythrocytes) in a young girl with acute lymphocytic leukemia. The level of 6-thioguanine nucleotide in the patient's erythrocytes was seven times the Population Median value, and she had intolerable hematologic toxic effects during postremission therapy with a standard dosage of mercaptopurine (75 mg/m 2 per day). Subsequent therapy with 6% of this dosage (10 mg/m 2 three times weekly) yielded erythrocytic 6-thioguanine nucleotide concentrations consistently above the Population Median but not associated with prohibitively toxic effects. This case demonstrates that thiopurine methyltransferase deficiency does not absolutely contraindicate mercaptopurine therapy, and it also provides insight into the mechanism of excessive toxic effects of mercaptopurine sometimes observed in children with acute lymphocytic leukemia.

Jean-françois Bernard - One of the best experts on this subject based on the ideXlab platform.

  • noxious stimulation excites serotonergic neurons a comparison between the lateral paragigantocellular reticular and the raphe magnus nuclei
    Pain, 2013
    Co-Authors: Caroline Sevozcouche, Michel Hamon, Jean-françois Bernard
    Abstract:

    The present study was designed to record electrophysiological responses to graded noxious thermal stimuli of serotonergic and nonserotonergic neurons in the lateral paragigantocellular reticular (LPGi) and the raphe magnus (RMg) nuclei in rats. All of the neurons recorded were juxtacellularly filled with neurobiotin and identified with double immunofluorescent labeling for both neurobiotin and serotonin. Under halothane anesthesia (0.75%), noxious thermal stimuli ⩾48°C activated almost all (88%) of the serotonergic neurons located within the LPGi (n = 16). The increase in firing was clear (3.4 ± 0.3 spike/s: mean of responses above the Population Median) and sustained during the whole application of strong thermal noxious stimuli, with a high mean threshold (48.3 ± 0.3°C) and large receptive fields. Recording of serotonergic neurons in the RMg (n = 21) demonstrated that the proportion of strongly activated (>2 spike/s) neurons (19% vs 59% for the LPGi) as well as the magnitude of the activation (2.1 ± 0.4 spike/s: mean of responses above the Population Median) to thermal noxious stimuli were significantly lower than in the LPGi (P < .05). Within the boundaries of both the LPGi and the RMg (B3 group), nonserotonergic neurons were also predominantly excited (75%) by noxious stimuli, and the resulting activation (7.9 ± 1.2 spike/s) was even greater than that of serotonergic neurons. Thermal noxious stimuli–induced activation of LPGi serotonergic cells probably plays a key role in serotonin-mediated modulations of cardiac baroreflex and transmission of nociceptive messages occurring under such intense noxious conditions.

  • Noxious stimulation excites serotonergic neurons: A comparison between the lateral paragigantocellular reticular and the raphe magnus nuclei
    Pain, 2012
    Co-Authors: Remi Gau, Caroline Sévoz-couche, Michel Hamon, Jean-françois Bernard
    Abstract:

    The present study was designed to record electrophysiological responses to graded noxious thermal stimuli of serotonergic and nonserotonergic neurons in the lateral paragigantocellular reticular (LPGi) and the raphe magnus (RMg) nuclei in rats. All of the neurons recorded were juxtacellularly filled with neurobiotin and identified with double immunofluorescent labeling for both neurobiotin and serotonin. Under halothane anesthesia (0.75%), noxious thermal stimuli ⩾48°C activated almost all (88%) of the serotonergic neurons located within the LPGi (n=16). The increase in firing was clear (3.4±0.3spike/s: mean of responses above the Population Median) and sustained during the whole application of strong thermal noxious stimuli, with a high mean threshold (48.3±0.3°C) and large receptive fields. Recording of serotonergic neurons in the RMg (n=21) demonstrated that the proportion of strongly activated (>2spike/s) neurons (19% vs 59% for the LPGi) as well as the magnitude of the activation (2.1±0.4spike/s: mean of responses above the Population Median) to thermal noxious stimuli were significantly lower than in the LPGi (P

William E Evans - One of the best experts on this subject based on the ideXlab platform.

  • altered mercaptopurine metabolism toxic effects and dosage requirement in a thiopurine methyltransferase deficient child with acute lymphocytic leukemia
    The Journal of Pediatrics, 1991
    Co-Authors: Mark W Roberts, Michelle Horner, D K Kalwinsky, William E Evans
    Abstract:

    Thiopurine methyltransferase deficiency, inherited as an autosomal codominant trait, is associated with aberrant mercaptopurine metabolism leading to excessive cellular accumulation of 6-thioguanine nucleotides, the active metabolites of mercaptopurine. We describe a case of severe thiopurine methyltransferase deficiency (activity 8 erythrocytes) in a young girl with acute lymphocytic leukemia. The level of 6-thioguanine nucleotide in the patient's erythrocytes was seven times the Population Median value, and she had intolerable hematologic toxic effects during postremission therapy with a standard dosage of mercaptopurine (75 mg/m 2 per day). Subsequent therapy with 6% of this dosage (10 mg/m 2 three times weekly) yielded erythrocytic 6-thioguanine nucleotide concentrations consistently above the Population Median but not associated with prohibitively toxic effects. This case demonstrates that thiopurine methyltransferase deficiency does not absolutely contraindicate mercaptopurine therapy, and it also provides insight into the mechanism of excessive toxic effects of mercaptopurine sometimes observed in children with acute lymphocytic leukemia.

Richa Mittal - One of the best experts on this subject based on the ideXlab platform.

  • Searching effective rotation patterns for Population Median using exponential type estimators in two-occasion rotation sampling
    Communications in Statistics - Theory and Methods, 2015
    Co-Authors: Kumari Priyanka, Richa Mittal
    Abstract:

    The present article is an attempt to explore the rotation patterns using exponential ratio type estimators for the estimation of finite Population Median at current occasion in two occasion rotatio...

  • A class of estimators for Population Median in two occasion rotation sampling
    Hacettepe Journal of Mathematics and Statistics, 2014
    Co-Authors: Kumari Priyanka, Richa Mittal
    Abstract:

    The present work deals with the problem of estimation of finite Population Median at current occasion, in two occasion successive (rotation) sampling. A class of estimators has been proposed for the estimation of Population Median at current occasion, which includes many existing estimators as a particular case. Asymptotic properties including the asymptotic convergence of proposed class of estimators are elaborated. Optimum replacement strategies are also discussed. The proposed class of estimators at optimum condition is compared with the sample Median estimator when there is no matching from the previous occasion as well as with some other members of the class. Theoretical results have been justified through empirical interpretation with the help of some natural Populations. 2000 AMS Classification: 62D05

  • Effective Rotation Patterns for Median Estimation in Successive Sampling
    Statistics in Transition New Series, 2014
    Co-Authors: Kumari Priyanka, Richa Mittal
    Abstract:

    The present work deals with the problem of estimation of Population Median at current occasion in two-occasion successive sampling. Best linear unbiased estimators have been proposed by utilizing additional auxiliary information, readily available on both the occasions. Asymptotic variances of the proposed estimators are derived and the optimum replacement policies are discussed. The behaviours of the proposed estimators are analyzed on the basis of data from natural Populations. Simulation studies have been carried out to measure the precision of the proposed estimators