Search results for "Field method"
showing 3 items of 33 documents
De la encuesta a la base de datos: experiencia de trabajo de campo del estudio «Inmigración, trabajo y salud» (Proyecto ITSAL)
2011
Objective: Despite the need for information in the area of migration and health, the available data are sparse. We describe the field work in a cross-sectional study on the health of immigrant workers in Spain. Method: A convenience sample of workers from Colombia, Ecuador, Morocco and Rumania in four cities was targeted, using a block-walking approach. The outcome rates of the American Association of Public Opinion Research were estimated. Results: Of 6,504 persons approached, 71.4% were eligible contacts. Of these contacts, only 57.8% completed interviews. Response and cooperation rates were above 50%. Conclusions: Block-walking enabled surveyors to access difficult-to-reach groups. The u…
From questionnaire to database: field work experience in the "Immigration, work and health survey" (ITSAL Project) De la encuesta a la base de datos:…
2011
Objective: Despite the need for information in the area of migration and health, the available data are sparse. We describe the field work in a cross-sectional study on the health of immigrant workers in Spain. Method: A convenience sample of workers from Colombia, Ecuador, Morocco and Rumania in four cities was targeted, using a block-walking approach. The outcome rates of the American Association of Public Opinion Research were estimated. Results: Of 6,504 persons approached, 71.4% were eligible contacts. Of these contacts, only 57.8% completed interviews. Response and cooperation rates were above 50%. Conclusions: Block-walking enabled surveyors to access difficult-to-reach groups. The u…
A gauge-technique Ansatz for the three gluon vertex of the background field method
2011
The vertex connecting one background gluon with two quantum ones constitutes a central ingredient in the gauge-invariant Schwinger-Dyson equation that determines the non-perturbative dynamics of the gluon propagator. This vertex satisfies a Ward identity with respect to the background gluon, and a Slavnov-Taylor identity with respect to the two quantum gluons. We present a complete Ansatz for this vertex, which satisfies both aforementioned identities. This entire construction depends crucially on a set of constraints relating the various form-factors of the ghost Green's functions appearing in the Slavnov-Taylor identity satisfied by the vertex. The validity of these constraints is demonst…