Randomization Test \u3cem\u3ep\u3c/em\u3e-Values versus Significance Levels

Bryan Manly responds to Richard Anderson\u27s article Conceptual Distinction between the Critical p Value and the Type I Error Rate in Permutation Testing

STATISTICS IN THE NEW MILLENNIUM: SOME PERSONAL VIEWS

In this paper I discuss three topics that I believe are relevant to the subject of statistics in the new millennium: (a) the impact of computers, and the state of computer-intensive methods as far as practical applications of statistics are concerned; (b) methods for the analysis of the extremely large data sets that are now becoming available; and (c) the use of statistics by scientists in general. For the first topic I suggest that the main advantage of computer-intensive methods is that they can under certain circumstances give simple and believable answers to questions when other methods fail. However, I caution against the uncritical use of computer power without proper checks that analyses work, particularly when conclusions are dependent on very complicated models with many assumptions that are difficult or impossible to verify. For the second topic I note that statistics grew up as a means of extracting the maximum amount of information from small sets of data, and we are now having some difficulty in adapting methods to huge data sets because sometimes the analyses that we might want to do are not possible even with today\u27s powerful computers. I discuss this particularly in terms of the analysis of resource selection data by animals where geographical information system data are available to describe what is available for animals to use. For the third topic I suggest that statistics and statisticians have something of an \u27image\u27 problem with scientists in general. Many scientists do not appear to regard statistics as important for their discipline, and yet errors in the analysis and interpretation of data seem to be fairly common in the scientific literature

From Late Prehistory to the Foundation of Early States in Inland Southeast Asia: a Debate

Mortuary data from three Iron Age sites in Northeast Thailand and three in Northwest Cambodia are here reviewed for information on social formation on the cusp of early states. It has been suggested that the three Cambodian sites present evidence for a complex polity with three social tiers and that this contrasts with the lack of any evidence for equivalent complexity in the three communities in the upper Mun Valley of Northeast Thailand. This model is examined and queried on the basis of insufficient data for the Cambodian sites, and contestable statistical analysis. In its place, an alternative is presented, that identifies a critically important climatic deterioration causing increased aridity which stimulated the development of plough-based wet rice cultivation in irrigated permanent fields. In the upper Mun Valley of Northeast Thailand, this coincided with a swift rise in social elites, interred in lineage-based nuclei in which leading individuals were accompanied by unprecedented wealth. Within a century or two, some Iron Age settlements greatly expanded into regal centers documented through texts that mentioned the state of Sri Canasapura. This transition might also have occurred in Northwest Cambodia at the same time, but evidence for this is so far unconvincing

Comparation of logistic regression methods and discrete choice model in the selection of habitats

Baseado em revisão mais recente de análises de dados em seleção de recurso pelos animais e com as mais recentes sugestões, que indicam a falta de uma teoria estatística unificada que mostre como a seleção do recurso pode ser detectada e medida, os autores sugerem que o conceito da função da seleção do recurso (RSF) pode ser a base do desenvolvimento da teoria. A revisão de modelos de escolha discreta (DCM) é sugerida como uma aproximação para estimar a RSF quando a escolha do animal os grupos de animais envolvem diferentes conjuntos de unidades de recurso disponíveis. A definição do RSF requer que o recurso que esteja sendo estudado consista em unidades discretas. O método estatístico frequentemente usado para estimar a RSF é a regressão logística mas DCM também pode ser usado. A teoria de DCM tem sido bem desenvolvida para análises de conjunto de dados que envolvem escolhas de produtos pelos humanos, mas também pode ser aplicável a escolhas de habitat pelos animais com algumas modificações. A comparação da regressão logística com o DCM para uma escolha é feita porque as estimativas do coeficiente do modelo de regressão logística inclui o intercepto, mas no DCM o coeficiente do intercepto não está presente. O objetivo deste trabalho foi comparar as estimativas da função da seleção do recurso obtida pela aplicação da regressão logística e o DCM do conjunto de dados de um estudo de seleção de habitat da coruja manchada (Strix occidentalis) no noroeste dos Estados Unidos.Based on a review of most recent data analyses on resource selection by animals as well as on recent suggestions that indicate the lack of an unified statistical theory that shows how resource selection can be detected and measured, the authors suggest that the concept of resource selection function (RSF) can be the base for the development of a theory. The revision of discrete choice models (DCM) is suggested as an approximation to estimate the RSF when the choice of animal or groups of animals involves different sets of available resource units. The definition of RSF requires that the resource which is being studied consists of discrete units. The statistical method often used to estimate the RSF is the logistic regression but DCM can also be used. The theory of DCM has been well developed for the analysis of data sets involving choices of products by humans, but it can also be applicable to the choice of habitat by animals, with some modifications. The comparison of the logistic regression with the DCM for one choice is made because the coefficient estimates of the logistic regression model include an intercept, which are not presented by the DCM. The objective of this work was to compare the estimates of the RSF obtained by applying the logistic regression and the DCM to the data set on habitat selection of the spotted owl (Strix occidentalis) in the north west of the United States

Polar Bear Aerial Survey in the Eastern Chukchi Sea: A Pilot Study

Alaska has two polar bear populations: the Southern Beaufort Sea population, shared with Canada, and the Chukchi/Bering Seas population, shared with Russia. Currently a reliable population estimate for the Chukchi/Bering Seas population does not exist. Land-based aerial and mark-recapture population surveys may not be possible in the Chukchi Sea because variable ice conditions, the limited range of helicopters, extremely large polar bear home ranges, and severe weather conditions may limit access to remote areas. Thus line-transect aerial surveys from icebreakers may be the best available tool to monitor this polar bear stock. In August 2000, a line-transect survey was conducted in the eastern Chukchi Sea and western Beaufort Sea from helicopters based on a U.S. Coast Guard icebreaker under the "Ship of Opportunity" program. The objectives of this pilot study were to estimate polar bear density in the eastern Chukchi and western Beaufort Seas and to assess the logistical feasibility of using ship-based aerial surveys to develop polar bear population estimates. Twenty-nine polar bears in 25 groups were sighted on 94 transects (8257 km). The density of bears was estimated as 1 bear per 147 km² (CV = 38%). Additional aerial surveys in late fall, using dedicated icebreakers, would be required to achieve the number of sightings, survey effort, coverage, and precision needed for more effective monitoring of population trends in the Chukchi Sea.L'Alaska a deux populations d'ours polaires : celle du sud de la mer de Beaufort, commune avec le Canada, et celle de la mer des Tchouktches / mer de Béring, commune avec la Russie. À l'heure actuelle, on ne possède pas d'estimation fiable de la population de la mer des Tchouktches / mer de Béring. En raison des conditions variables de la glace, de la portée limitée des hélicoptères, de la très grande étendue du domaine vital de l'ours polaire et des conditions météorologiques particulièrement mauvaises - facteurs qui limitent l'accès aux régions éloignées -, il n'est peut-être pas possible d'effectuer des relevés aériens à base terrestre de la population ou des relevés par marquage-recapture. Le meilleur outil disponible pour une surveillance continue de cette population d'ours polaires semble donc être le relevé de transects effectué depuis les airs par un appareil embarqué sur un brise-glace. En août 2000, un relevé de transect a été effectué dans l'est de la mer des Tchouktches et dans l'ouest de la mer de Beaufort depuis des hélicoptères embarqués sur un brise-glace de la garde côtière américaine sous les auspices du programme des navires de passage. Les objectifs de cette étude pilote étaient d'estimer la densité de l'ours polaire dans l'est de la mer des Tchouktches et l'ouest de la mer de Beaufort, et d'évaluer la faisabilité logistique de l'utilisation d'hélicoptères embarqués pour établir des estimations de la population d'ours polaires. Vingt-neuf ours polaires répartis en 25 groupes ont été aperçus dans 94 transects (8257 km). La densité des ours était évaluée à 1 animal par 147 km² (CV = 38 %). Il faudrait réaliser d'autres relevés aériens à la fin de l'automne, en ayant recours à des brise-glace spécialisés, pour en arriver au nombre d'observations, aux activités de relevés, à la couverture et à la précision nécessaires à une surveillance plus efficace des tendances démographiques dans la mer des Tchouktches

Detecção de padrões espaciais na ocorrência do tripes (Thrips tabaci) na cultura da cebola

Onion (Allium cepa) is one of the most cultivated and consumed vegetables in Brazil and its importance is due to the large laborforce involved. One of the main pests that affect this crop is the Onion Thrips (Thrips tabaci), but the spatial distribution of this insect, although important, has not been considered in crop management recommendations, experimental planning or sampling procedures. Our purpose here is to consider statistical tools to detect and model spatial patterns of the occurrence of the onion thrips. In order to characterize the spatial distribution pattern of the Onion Thrips a survey was carried out to record the number of insects in each development phase on onion plant leaves, on different dates and sample locations, in four rural properties with neighboring farms under different infestation levels and planting methods. The Mantel randomization test proved to be a useful tool to test for spatial correlation which, when detected, was described by a mixed spatial Poisson model with a geostatistical random component and parameters allowing for a characterization of the spatial pattern, as well as the production of prediction maps of susceptibility to levels of infestation throughout the area.A cebola é uma das hortaliças mais cultivadas e consumidas no Brasil e sua importância social se deve à grande demanda por mão-de-obra. Uma das principais pragas que afeta essa cultura é o tripes do prateamento (Thrips tabaci) e sua distribuição espacial, embora importante, não tem sido considerada nas recomendações de manejo da cultura, planejamento de experimentos ou estudos amostrais. O objetivo desse artigo foi considerar métodos estatísticos para detectar e modelar padrões espaciais na ocorrência do tripes do prateamento da cebola. Para caracterizar o padrão espacial da dispersão do tripes do prateamento da cebola foi feito um levantamento anotando-se o número de insetos por fase de desenvolvimento em folhas de plantas de cebola, em diferentes datas e pontos amostrais dentro de quatro propriedades com fazendas vizinhas apresentando diferentes níveis de infestação e métodos de plantio. O teste de aleatorização de Mantel mostrou-se útil para testar a presença de padrão espacial, que quando detectado foi descrito por um modelo de Poisson misto espacial com componente aleatório geoestatístico com parâmetros que possibilititam a caracterização do padrão espacial, bem como a obtenção de mapas de predição dos níveis de susceptibilidade à infestação na área.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Spatial pattern detection modeling of thrips (Thrips tabaci) on onion fields

Onion (Allium cepa) is one of the most cultivated and consumed vegetables in Brazil and its importance is due to the large laborforce involved. One of the main pests that affect this crop is the Onion Thrips (Thrips tabaci), but the spatial distribution of this insect, although important, has not been considered in crop management recommendations, experimental planning or sampling procedures. Our purpose here is to consider statistical tools to detect and model spatial patterns of the occurrence of the onion thrips. In order to characterize the spatial distribution pattern of the Onion Thrips a survey was carried out to record the number of insects in each development phase on onion plant leaves, on different dates and sample locations, in four rural properties with neighboring farms under different infestation levels and planting methods. The Mantel randomization test proved to be a useful tool to test for spatial correlation which, when detected, was described by a mixed spatial Poisson model with a geostatistical random component and parameters allowing for a characterization of the spatial pattern, as well as the production of prediction maps of susceptibility to levels of infestation throughout the area.A cebola é uma das hortaliças mais cultivadas e consumidas no Brasil e sua importância social se deve à grande demanda por mão-de-obra. Uma das principais pragas que afeta essa cultura é o tripes do prateamento (Thrips tabaci) e sua distribuição espacial, embora importante, não tem sido considerada nas recomendações de manejo da cultura, planejamento de experimentos ou estudos amostrais. O objetivo desse artigo foi considerar métodos estatísticos para detectar e modelar padrões espaciais na ocorrência do tripes do prateamento da cebola. Para caracterizar o padrão espacial da dispersão do tripes do prateamento da cebola foi feito um levantamento anotando-se o número de insetos por fase de desenvolvimento em folhas de plantas de cebola, em diferentes datas e pontos amostrais dentro de quatro propriedades com fazendas vizinhas apresentando diferentes níveis de infestação e métodos de plantio. O teste de aleatorização de Mantel mostrou-se útil para testar a presença de padrão espacial, que quando detectado foi descrito por um modelo de Poisson misto espacial com componente aleatório geoestatístico com parâmetros que possibilititam a caracterização do padrão espacial, bem como a obtenção de mapas de predição dos níveis de susceptibilidade à infestação na área

The use of a multivariate statistical procedure in analysing the germination process of two bean cultivars, compared with a univariate approach

Abstract Several studies on plant physiology are aimed at describing or assessing seed germination processes under laboratory conditions. With respect to seed germination of crop species, some statistical complexities have been discussed, but they have not been developed much in practice. That is, such discussions are not as common as in other areas of plant biology. Additionally, the current literature that is concerned directly with the application of statistics in seed germination indicates that simple and well-known statistical procedures still merit further consideration. Regarding the use of multivariate statistical methods in agriculture, several field studies have used such procedures as a means of clarifying some underlying ecological principles that govern crop production. Nonetheless, multivariate tests have not been widely employed in germination experiments. Therefore, in the present study a simple multivariate statistical procedure (Hotelling's T 2 statistic) was utilised in order to compare two common bean cultivars, using germination indices as variables. The outcome derived from the multivariate approach was compared with that obtained from the utilisation of the univariate t test. The simultaneous application of both methods (that is, the classical univariate t test and the multivariate T 2 test) showed that the outcomes may well depend on the approach utilised