References of "Brostaux, Yves"
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See detailDevelopment and application of a microplate method to evaluate the efficacy of essential oils against Penicillium italicum Wehmer, Penicillium digitatum Sacc. and Colletotrichum musea (Berk. M.A. Curtis) Arx, three postharvest fungal pathogens of fruits
Kouassi, Kouadio Hugues Sosthène ULg; Bajji, M.; Brostaux, Yves ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(3), 325-336

A microbioassay was developed for evaluating the in vitro antifungal activity of 30 preselected essential oils. A template based on 10 serial dilutions with eight replicates per dilution arranged on two ... [more ▼]

A microbioassay was developed for evaluating the in vitro antifungal activity of 30 preselected essential oils. A template based on 10 serial dilutions with eight replicates per dilution arranged on two 96-well ELISA plates was used as a reproducible and standardized design to identify the in vitro effectiveness of these essential oils against Penicillium italicum Wehmer, Penicillium digitatum Sacc. and Colletotrichum musea (Berk. M.A. Curtis) Arx, three postharvest fungal pathogens, on fruits. Growth of mycelium was monitored by measuring optical density (492 nm). Cinnamomum zeylanicum, Cinnamomum verum and Eugenia caryophyllus were found to be still active against all the three pathogens even at 100 ppm. Compared to other methods, this microbioassay proved to be a rapid, reproducible, and efficient method for testing the efficacy of essential oils that inhibit spore germination in P. italicum, P. digitatum and C. musea. The assay requires relatively small amounts of essential oils. [less ▲]

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See detailPhenological patterns in a natural population of a tropical timber tree species, Milicia excelsa (Moraceae): evidence of Isolation By Time and its interaction with feeding strategies of dispersers
Daïnou, Kasso ULg; Laurenty, Eric; Mahy, Grégory ULg et al

in American Journal of Botany (2012), 99(9), 1-11

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to ... [more ▼]

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to flowering time (the so-called isolation by time, IBT). Since phenological processes can be subject to selection, the persistence of flowering asynchrony may be due to opposing selective pressures during mating, dispersal and regeneration phases. Our study aimed to investigate phenology, fruit-handling by animals and their interaction, in a timber tree species, Milicia excelsa. We analyzed phenological data collected over a 6-year period on 69 genotyped trees in a Cameroonian natural rainforest complemented by data from germination trials and field observations of dispersers. Initiation of flowering correlated with variation in temperature and relative humidity, but was also affected by genetic factors: pairwise differences in flowering time between nearby individuals correlated with kinship coefficient, and earliness of flowering remained stable over time. A decrease in mean seed production per fruit with increasing flowering time suggests selection against late bloomers. However, germination rate was not affected by seed collection date, and the main seed disperser, the bat Eidolon helvum, seemed to increase in abundance at the end of the reproductive season, and preferred trees in open habitats where early and late bloomers are expected. The pairwise approach performs well to detecting IBT. The persistence of different mating pools in such a case may result from a trade-off between selective forces during the mating and seed dispersal processes. [less ▲]

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See detailRole of long-chain hydrocarbons in the aggregation behaviour of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Brostaux, Yves ULg et al

in Journal of Insect Physiology (2012)

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the ... [more ▼]

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the induction of allergic reactions. Migratory flight and macrosite choice of this species is well documented. H. axyridis shows a hypsotactic behaviour and a clear preference for contrasting visual elements. However, how the microsite is selected remains undocumented, although a better understanding of the implicated factors could lead to the development of new control methods for this pest. In this work, we have hypothesized that non-volatile compounds are involved in the microsite choice and the aggregation process of this beetle. Long chain hydrocarbons were identified inside aggregation sites, comprising saturated and unsaturated homologues. An aggregation bioassay was then conducted on overwintering individuals, highlighting the retention capacity of the previously cited compounds on the tested ladybeetles. Additional investigations have shown that H. axyridis males and females, originating from overwintering sites, deposit a similar blend of molecules while walking. A Y-shaped tube assay revealed that this blend is used by male and female congeners as cue, allowing individuals to orientate towards the treated side of the olfactometer. These results suggest the use of two different blends of long chain hydrocarbons by H. axyridis during its aggregative period, the first one to lead conspecifics towards aggregation sites (microsites) and the second to ensure the cohesion of the aggregation. These findings support the potential use of these blends, in association with volatiles, in the design of traps in order to control infestations of this species in dwellings. [less ▲]

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See detailStudy of the factors involved in the aggregation of Harmonia axyridis Pallas (Coleoptera : Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

in Communications in Agricultural and Applied Biological Sciences (2012), 77(1), 101-104

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in ... [more ▼]

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in the selection of its aggregation sites. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregations and ensure the cohesion of the cluster. On the other hand, we investigated the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory highlighted a permanent aggregative behaviour of H. axyridis, even during non-wintering conditions, and the existence of social interactions between individuals. [less ▲]

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See detailOptimization of formic/acetic acid delignification of Miscanthus ×giganteus for enzymatic hydrolysis using response surface methodology
Vanderghem, Caroline ULg; Brostaux, Yves ULg; Jacquet, Nicolas ULg et al

in Industrial Crops & Products (2012), 35

A Box–Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus ×giganteus for ... [more ▼]

A Box–Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus ×giganteus for enzymatic hydrolysis. The effects of three independent variables, namely cooking time (1, 2 and 3 h), formic acid/acetic acid/water ratio (20/60/20, 30/50/20 and 40/40/20) and temperature (80, 90 and 107 ◦C) on pulp yield, residual Klason lignin content, concentration of degradation products (furfural and hydroxymethylfurfural) in the black liquor, and enzymatic digestibility of the pulps were investigated. The major parameter influencing was the temperature for pulp yield, delignification degree, furfural production and enzymatic digestibility. According to the response surface analysis the optimum conditions predicted for a maximum enzymatic digestibility of the glucan (75.3%) would be obtained using a cooking time of 3 h, at 107 ◦C and with a formic acid/acetic acid/water ratio of 40/40/20%. Glucan digestibility was highly dependent on the delignification degree. [less ▲]

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See detailThe ecological study of an unknown non-timber forest product (NTFP): the African walnut (Coula edulis Baill.)
Moupela, Christian ULg; Vermeulen, Cédric ULg; Lebailly, Philippe ULg et al

Conference (2011, November 15)

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux ... [more ▼]

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux de son écologie, dont le potentiel de production, la dispersion et la prédation des fruits, demeurent inconnus, ce qui pourrait constituer un frein à sa valorisation. L’étude s’est déroulée au Gabon et s’est attachée à quantifier la production fruitière de l’espèce et à identifier les prédateurs et disperseurs des fruits. Trente-neuf collecteurs circulaires ont été installés sous les houppiers, les données récoltées (nombre et masse des fruits) étant ensuite mises en relation avec le diamètre. Par ailleurs, sept semenciers ont fait l’objet d’observations indirectes grâce à un dispositif de caméras-pièges. Les premières fructifications apparaissent sur les semenciers à partir de 12,3 cm de diamètre. Elle se produit de janvier à avril. Les quantités de fruits sont corrélées positivement au diamètre (r² = 0,493 ; p = 0,001). Dix espèces animales ont été observées aux pieds des arbres en fruits, leur rôle dans la dynamique de population de l’espèce est potentiellement important. [less ▲]

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See detailThe ecological study of an unknown non-timber forest product (NTFP) : The African walnut (Coula edulis Baill.)
Moupela, Christian; Vermeulen, Cédric ULg; Brostaux, Yves ULg et al

Conference (2011, November)

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux ... [more ▼]

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux de son écologie, dont le potentiel de production et la prédation des fruits, demeurent inconnus, ce qui peut constituer un frein à sa valorisation. L’étude s’est déroulée au Gabon et s’est attachée à quantifier la production fruitière de l’espèce et à identifier les prédateurs potentiels des fruits. Trente-neuf collecteurs circulaires ont été installés sous les houppiers, les données récoltées (nombre et masse des fruits) étant ensuite mises en relation avec le diamètre. Par ailleurs, sept semenciers ont fait l’objet d’observations indirectes grâce à un dispositif de caméras-pièges. Le diamètre minimum de fertilité est de 12,3 cm, tandis que 23 cm dhp constitue pour l’espèce le diamètre effectif de fructification. Celle-ci se produit de décembre à avril. Les quantités de fruits sont corrélées positivement au diamètre. Dix espèces animales ont été observées aux pieds des arbres en fruits, leur rôle dans la dynamique de l’espèce est potentiellement important. [less ▲]

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See detailInférence statistique et critères de qualité de l'ajustement en régression logistique binaire
Palm, Rodolphe ULg; Brostaux, Yves ULg; Claustriaux, Jean-Jacques ULg

in Notes de Statistique et d'Informatique (2011), (5), 32

The principles of statistical inference based on the maximum likelihood function are described and applied to binary logistic regression. Several goodness of fit statistics are also given. These topics ... [more ▼]

The principles of statistical inference based on the maximum likelihood function are described and applied to binary logistic regression. Several goodness of fit statistics are also given. These topics are illustrated by an example processed by Minitab and SAS softwares. [less ▲]

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See detailLa régression logistique avec Minitab
Palm, Rodolphe ULg; Brostaux, Yves ULg

in Notes de Statistique et d'Informatique (2011), (4), 15

This note describes the Minitab commands BLOGISTIC, NLOGISTIC and OLOGISTIC and proposes a macro, which can be downloaded, for coding the data in order to fit the continuation-ratio logits model. The ... [more ▼]

This note describes the Minitab commands BLOGISTIC, NLOGISTIC and OLOGISTIC and proposes a macro, which can be downloaded, for coding the data in order to fit the continuation-ratio logits model. The commands are illustrated by an example. [less ▲]

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See detailInfluence of the processing parameters on the physicochemical properties of puff pastry margarines
Lefebure, Emilie ULg; Ronkart, Sébastien; Brostaux, Yves ULg et al

Poster (2011, September 18)

Margarinespresentdifferentphysicalpropertieswithrespecttotheirpurposedapplication.Forexample,aspecialtypeoffatisrequiredforpreparationofpuffpastry.Puffpastrymargarines(PPMs)havetobeveryfirmandplastic ... [more ▼]

Margarinespresentdifferentphysicalpropertieswithrespecttotheirpurposedapplication.Forexample,aspecialtypeoffatisrequiredforpreparationofpuffpastry.Puffpastrymargarines(PPMs)havetobeveryfirmandplastic.Therequiredphysicalpropertiesarethusobtainedbyprocessingsuitablyselectedblendsoffatsandoils.Thisstudyfocusesontheinfluenceofprocessingparametersonphysicochemicalpropertiesofpuffpastrymargarine.Forthispurpose,twoselectedfatblendswereconsidered(bothpalm-based):onewaslow-trans(0.5%)andtheotherwastrans-free. [less ▲]

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See detailDetection of aggregative behaviour in binary choice experiments
Brostaux, Yves ULg

Poster (2011, August 22)

Aggregative behaviour can be defined as a natural tendency for individuals to cluster in space into groups of varying sizes. In entomology, this behaviour can be detected in binary choice experiments ... [more ▼]

Aggregative behaviour can be defined as a natural tendency for individuals to cluster in space into groups of varying sizes. In entomology, this behaviour can be detected in binary choice experiments. Analysis of these experiments reveals specific characteristics (unequal counts between repetitions, dependence of individual choices) that make the traditional adjustment tests fail. We demonstrate that the use of generalized linear models can circumvent these pitfalls and deliver a reliable diagnosis on the social behaviour of the studied invertebrates. The strength of this behaviour can then be evaluated through the use of common correlation models. [less ▲]

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See detailChemical and physical factors involved in the aggregation behaviour of Harmonia axyridis Pallas
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

Conference (2011, July 27)

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See detailCarrion beetles visiting pig carcasses during early spring in urban, forest and agricultural biotopes of Western Europe
Dekeirsschieter, Jessica ULg; Verheggen, François ULg; Haubruge, Eric ULg et al

in Journal of Insect Science [=JIS] (2011), 11

Carrion beetles are important in terrestrial ecosystems, consuming dead mammals and promoting the recycling of organic matter into ecosystems. Most forensic studies are focused on succession of Diptera ... [more ▼]

Carrion beetles are important in terrestrial ecosystems, consuming dead mammals and promoting the recycling of organic matter into ecosystems. Most forensic studies are focused on succession of Diptera while neglecting Coleoptera. So far, little information is available on carrion beetles postmortem colonization and decomposition process in temperate biogeoclimatic countries. These beetles are however part of the entomofaunal colonization of a dead body. Forensic entomologists need databases concerning the distribution, ecology and phenology of necrophagous insects, including silphids. Forensic entomology uses pig carcasses to surrogate human decomposition and to investigate entomofaunal succession. However, few studies have been conducted in Europe on large carcasses. The work reported here monitored the presence of the carrion beetles (Coleoptera: Silphidae) on decaying pig carcasses in three selected biotopes (forest, crop field, urban site) at the beginning of spring. Seven species of Silphidae were recorded: Nicrophorus humator (Gleditsch), Nicrophorus vespillo (L.), Nicrophorus vespilloides (Herbst), Necrodes littoralis L., Oiceoptoma thoracica L., Thanatophilus sinuatus (Fabricius), Thanatophilus rugosus (L.). All of these species were caught in the forest biotope, and all but O. thoracica were caught in the agricultural biotope. No silphids were caught in the urban site [less ▲]

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See detailMicroorganisms from Aphid Honeydew Attract and Enhance the Efficacy of Natural Enemies
Leroy, Pascal ULg; Sabri, Ahmed ULg; Heuskin, Stéphanie ULg et al

in Nature Communications (2011), 2

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their ... [more ▼]

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their dispersal in natural environment. Here we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which acts as a kairomone enhancing the efficiency of aphid natural enemies. Our findings represent the first case of a host-associated bacterium driving prey location and ovipositional preference for the natural enemy. We show that this bacterium has a key role in tritrophic interactions because it is the direct source of volatiles used to locate prey. Some specific semiochemicals produced by S. sciuri were also identified as significant attractants and ovipositional stimulants. The use of this host-associated bacterium could certainly provide a novel approach to control aphids in field and greenhouse systems. [less ▲]

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See detailA semiochemical enhancing the attractiveness of aphidophagous predators in potato crops
Leroy, Pascal ULg; Vandereycken, Axel ULg; Sabri, Ahmed ULg et al

Poster (2011, May 24)

Aphids are major pests of crops worldwide and the use of pesticides has led to resistant populations. The integration of aphid natural enemies in integrated management programs could be an option, but ... [more ▼]

Aphids are major pests of crops worldwide and the use of pesticides has led to resistant populations. The integration of aphid natural enemies in integrated management programs could be an option, but their efficacy is often limited by their quick dispersal from the ecosystem where they are released. Here, using wind-tunnel and field experiments, we have demonstrated that 3-Methyl-2-butenal acts as an efficient attractant and ovipositional stimulant for the hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae), enhancing its efficiency as biological control agent in crop fields. Wind-tunnel assays allowed determining that a minimal dose of 250 µg of 3-Methyl-2-butenal is required to attract the hoverflies over a distance of 2.5 m while a minimal dose of 500 µg is needed to induce the oviposition. Both attraction and oviposition increased proportionally to the tested doses showing that hoverflies are able to regulate their oviposition according to the chemical stimuli from their environment. In field experiments, both Syrphidae and Chrysopidae were strongly attracted by the 3-Methyl-2-butenal at a dose of 10 mg which also induces the oviposition of these two aphid predators in potato crops. This study also highlighted that hoverflies are the most abundant aphid predators found in natural environment. Against aphids, the use of this semiochemical could certainly enhance the efficiency of natural enemies. Furthermore, the use of the chemical cue 3-Methyl-2-butenal could provide a novel approach to control aphids in field and greenhouse systems. [less ▲]

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See detailMicroorganisms from aphids attract hoverflies and enhance their efficacy
Leroy, Pascal ULg; Sabri, Ahmed ULg; Heuskin, Stéphanie ULg et al

Poster (2011, March 05)

Aphids are some of the most serious pests of crops worldwide, causing major yield and economic losses. They damage plants by feeding on the phloem sap, excreting copious amounts of honeydew and, in some ... [more ▼]

Aphids are some of the most serious pests of crops worldwide, causing major yield and economic losses. They damage plants by feeding on the phloem sap, excreting copious amounts of honeydew and, in some cases, vectoring plant diseases. Here, we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which is involved in the release of semiochemicals acting as a kairomone for aphid natural enemies. These semiochemicals were identified by Solid-Phase Microextraction (SPME) and Gas Chromatography-Mass Spectrometry (GC-MS). Our results show that this bacterium plays a key role in the interactions between aphids and natural enemies because it is the direct source of volatiles used by the aphidophagous hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae) to locate its aphid prey. Through wind-tunnel experiments, some specific semiochemicals produced by S. sciuri were identified as significant attractants and ovipositional stimulants. Also, assays under greenhouses and in potato fields have demonstrated that a culture medium containing the bacterium S. sciuri strongly attracts and induces the oviposition of hoverflies, enhancing their efficiency as biological control agents. The use of this no pathogenic bacterium could provide a very novel approach towards enhancing the efficacy of biological control agents to control aphids in field crops and greenhouse systems. [less ▲]

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See detailMacros Minitab pour le choix d'une transformation pour la normalisation de variables
Palm, Rodolphe ULg; Brostaux, Yves ULg; Claustriaux, Jean-Jacques ULg

in Notes de Statistique et d'Informatique (2011), (3),

Macros are proposed to Minitab users for transforming data to normality. The following transformations are examined : log transformation, Box et Cox transformation with lambda equal to -2, -1, -0,5, 0,5 ... [more ▼]

Macros are proposed to Minitab users for transforming data to normality. The following transformations are examined : log transformation, Box et Cox transformation with lambda equal to -2, -1, -0,5, 0,5 and 2, Box et Cox transformation with maximum likelihood estimation of lambda and transformations using the Johnson system of distributions. Two examples are given. [less ▲]

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See detailEvaluation d’une méthode d’échantillonnage passif pour la mesure des monoterpènes dans l’air intérieur
Marlet, Christelle ULg; Lognay, Georges ULg; Plaisance, Hervé et al

in Pollution Atmosphérique (2011), 210

Monoterpenes are compounds naturally emitted by wooden materials. A preliminary study had demonstrated the occurrence of some monoterpenes in the timber frame constructions. Contrary to the active ... [more ▼]

Monoterpenes are compounds naturally emitted by wooden materials. A preliminary study had demonstrated the occurrence of some monoterpenes in the timber frame constructions. Contrary to the active sampling, the passive sampling with Radiello® device simplifies the sampling step that is an interest in indoor environment. However, the knowledge of the sampling rate is necessary for quantification via the passive samplers Radiello®. Radiello® sampler with Tenax TA cartridge was evaluated for the 4-h concentration measurements of nine monoterpenes (α-pinene, β-pinene, d-limonene, Δ3-carene, camphene, carvone, 1,8-cineole, linalool and p-cymene). The performance parameters of the method (calibration curve, trueness, repeatability, blank level, stability of samples) were estimated. The sampling rates were first evaluated under the standard conditions in an exposure chamber. The influences of three environmental factors (temperature (T), relative humidity (RH) and concentration level (C)) on the sampling rates were also evaluated following a full factorial design at two factor levels (low and high). The monoterpenes concentrations in the exposure chamber were followed by an active sampling on tube Tenax TA. For both sampling devices, analyses were realized by TD-GC-MS. The results of this study demonstrated that the Radiello® device is suitable for the measurement of 5 of 9 studied monoterpenes. The sampling rates were defined by an equation including two factors, temperature and relative humidity. Temperature is found to be the most important factor leading to variability of the all monoterpene sampling rates. An equation allowing to estimate the sampling rate was established for every studied compound. Measurements of monoterpenes with the Radiello® device were then carried out on new wooden houses and compared with measurements obtained by active sampling on Tenax TA tubes. [less ▲]

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See detailCalculating and Reporting Managed Honey Bee Colony Losses
vanEngelsdorp, Dennis; Brodschneider, Robert; Brostaux, Yves ULg et al

in Yoder, Jay (Ed.) Honey Bee Colony Health (2011)

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See detailPrincipaux modèles utilisés en régression logistique
Gillet, Adeline; Brostaux, Yves ULg; Palm, Rodolphe ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(3), 425-433

Regression is a commonly used technique for describing the relationship between a response variable and one or more explanatory variables. When the response variable is a categorical variable, usual ... [more ▼]

Regression is a commonly used technique for describing the relationship between a response variable and one or more explanatory variables. When the response variable is a categorical variable, usual regression based on ordinary least squares should be replaced by logistic regression. Binary logistic regression should be used to perform a regression on a dichotomous response. Nominal polytomous logistic regression applies to a categorical response variable that has more than two levels with a natural ordering. And ordinal polytomous logistic regression is used when the response is a categorical variable that has more than two levels with a natural ordering. This note gives an overview of these logistic regression methods and describes three models commonly used when performing ordinal logistic regression. These models are illustrated by an example related to oak decline in the Walloon Region (Belgium). [less ▲]

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