Properties of design-based estimation under stratified spatial sampling with application to canopy coverage estimation

The estimation of the total of an attribute defined over a continuous planar domain is required in many applied settings, such as the estimation of canopy coverage in the Monterano Nature Reserve in Italy. If the design-based approach is considered, the scheme for the placement of the sample sites over the domain is fundamental in order to implement the survey. In real situations, a commonly adopted scheme is based on partitioning the domain into suitable strata, in such a way that a single sample site is uniformly placed (i.e., selected with uniform probability density) in each stratum and sample sites are independently located. Under mild conditions on the function representing the target attribute, it is shown that this scheme gives rise to an unbiased spatial total estimator which is "superefficient" with respect to the estimator based on the uniform placement of independent sample sites over the domain. In addition, the large-sample normality of the estimator is proven and variance estimation issues are discussed.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS509 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

How are Statistical Journals linked? A Network Analysis

The exploratory analysis developed in this paper relies on the hypothesis that each editor possesses some power in the definition of the editorial policy of her journal. Consequently if the same scholar sits on the board of two journals, those journals could have some common elements in their editorial policies. The proximity of the editorial policies of two scientific journals can be assessed by the number of common editors sitting on their boards. A database of all editors of the journals classified as “Statistics & Probability” in the Journal of Citation Report by ISI-Thomson is used. The structure of the network generated by the interlocking editorship is explored applying the instruments of network analysis. Evidences are found of a very compact network. This is interpreted as the result of a common perspective about the appropriate methods for investigating the problems and constructing the theories in the domain of statisticsNetworks; Journals; Editorial boards; Interlocking editorship; Statisticians

A family of consistent normally distributed tests for Poissonity

A consistent test based on the probability generating function is proposed for assessing Poissonity against a wide class of count distributions, which includes some of the most frequently adopted alternatives to the Poisson distribution. The statistic, in addition to have an intuitive and simple form, is asymptotically normally distributed, allowing a straightforward implementation of the test. The finite sample properties of the test are investigated by means of an extensive simulation study. The test shows a satisfactory behaviour compared to other tests with known limit distribution

Design-based spatial interpolation with data driven selection of the smoothing parameter

In the inverse distance weighting interpolation the interpolated, value is a weighted mean of the sampled values, with weights decreasing with the distances. The most widely adopted class of distance functions is the class of negative powers of order α and the appropriate choice of the smoothing parameter α is a crucial issue. In this paper, we give sufficient conditions for the design-based consistency of the inverse distance weighting interpolator when α is selected by cross-validation techniques, and a pseudo-population bootstrap approach is introduced to estimate the accuracy of the resulting interpolator. A simulation study is performed to empirically confirm the theoritical findings and to investigate the finite-sample properties of the interpolator obtained using leave-one-out cross-validation. Moreover, a comparison with the nearest neighbor interpolator, which is the limiting case for α = ∞, is performed. Finally, the estimation of the surface of the Shannon diversity index of tree diameter at breast height in the experimental watershed of Bonis forest (Southern Italy) is described

Goodness-of-fit test for count distributions with finite second moment

A goodness-of-fit test for one-parameter count distributions with finite second moment is proposed. The test statistic is derived from the $L_1$-distance of a function of the probability generating function of the model under the null hypothesis and that of the random variable actually generating data, when the latter belongs to a suitable wide class of alternatives. The test statistic has a rather simple form and it is asymptotically normally distributed under the null hypothesis, allowing a straightforward implementation of the test. Moreover, the test is consistent for alternative distributions belonging to the class, but also for all the alternative distributions whose probability of zero is different from that under the null hypothesis. Thus, the use of the test is proposed and investigated also for alternatives not in the class. The finite-sample properties of the test are assessed by means of an extensive simulation study

Early progression as a predictor of survival in marginal zone lymphomas: An analysis from the FIL-NF10 study

Marginal zone lymphomas (MZLs) are indolent nonfollicular B-cell lymphomas (INFLs) and have heterogeneous clinical behavior. Recently, time to progression of disease at 24 months (POD24) was identified to stratify overall survival (OS) in follicular non-Hodgkin lymphoma and in INFL. Here, we examined the ability of POD24 to predict subsequent OS in a large, international cohort of MZL as part of the NF10 prospective international registry headed by Fondazione Italiana Linfomi (FIL). POD24 was only calculated for MZL patients requiring immediate therapy and was defined as experiencing lymphoma progression within 24 months from diagnosis. Among the 1325 patients enrolled in the NF10 study, we identified 321 patients with MZL for whom immediate therapy was planned right after lymphoma diagnosis. Overall, POD24 was confirmed in 59 patients (18%). Three-year OS for patients with POD24 was 53% with a hazard ratio of 19.5 (95% confidence interval, 8.4-45) compared with patients without POD24 (3-year OS, 95%). Association of POD24 with OS was confirmed for the subgroup of splenic and extranodal MZLs. Assessment of POD24 stratifies subsequent outcome inMZL and identifies a high-risk population