Efficient balanced sampling: The cube method

A balanced sampling design is defined by the property that the Horvitz-Thompson estimators of the population totals of a set of auxiliary variables equal the known totals of these variables. Therefore the variances of estimators of totals of all the variables of interest are reduced, depending on the correlations of these variables with the controlled variables. In this paper, we develop a general method, called the cube method, for selecting approximately balanced samples with equal or unequal inclusion probabilities and any number of auxiliary variable

Intermediate-term results after en bloc double-lung transplantation with bronchial arterial revascularization

AbstractObjective: Between May 1990 and January 1994, 18 patients underwent en bloc double-lung transplantation with tracheal anastomosis and bronchial arterial revascularization. Because at that time it was already suggested that chronic ischemia could be a contributing factor in occurrence of obliterative bronchiolitis, the purpose of this study was to evaluate, with a follow-up ranging from 22 to 69 months, the midterm effects of bronchial arterial revascularization on development of obliterative bronchiolitis. Results: Results were assessed according to tracheal healing, functional results, rejection, infection, and incidence of obliterative bronchiolitis. There were no intraoperative deaths or reexplorations for bleeding related to bronchial arterial revascularization, but there were three hospital deaths and five late deaths, two of them related to obliterative bronchiolitis. According to the criteria previously defined, tracheal healing was assessed as grade I, IIa, or IIb in 17 patients and grade IIIa in only one patient. Early angiography (postoperative days 20 to 40) demonstrated a patent graft in 11 of the 14 patients in whom follow-up information was obtained. Ten patients are currently alive with a 43-month mean follow-up. Among the 15 patients surviving more than 1 year, functional results have been excellent except in five in whom obliterative bronchiolitis has developed and who had an early or late graft thrombosis. Furthermore, those patients had a significantly higher incidence of late acute rejection (p < 0.02), cytomegalovirus disease (p < 0.006), and bronchitis episodes (p < 0.0008) than patients free from obliterative bronchiolitis. Conclusion: We conclude that besides its immediate beneficial effect on tracheal healing, long-lasting revascularization was, at least in this small series, associated with an absence of obliterative bronchiolitis, thus suggesting but not yet proving the possible role of chronic ischemia in this multifactorial disease. (J THORAC CARDIOVASC SURG 1996;112:1292-300

Methodology of Correcting Nonresponse Bias: Introducing Another Bias? The Case of the Swiss Innovation Survey 2002

The non-response in a survey can lead to severe bias. In order to manage this problem, it is usual to make a second survey by a sample of non-respondent. This allows us to test if there is a significant difference in the key variables of the survey between respondents and nonrespondents and, if yes, to take it into account. But, the risk is great to introduce another bias depending on the mode (mail vs phone) of survey. The KOF industrial economics group is exploring for many years the innovation behaviour of Swiss firms using a mail survey addressed to almost 6600 panel firms of the industrial, construction and service sector. We use since some years the data of a second survey by nonrespondents to correct non-response bias. Contrarily to the first survey, this one is made by phone. One can suspect that the personal interaction with the person(s) calling may be introducing another bias. In order to investigate this question, in the case of the ETH Zurich's innovation 2002 survey, we decided next to the regular non-respondent-phone-survey, to conduct a similar phone survey by a subsample of the respondent-group. Thus, we dispose of data for the same variables coming from the two modes of survey and allowing us to show if there is a difference or not in the response behaviour. We use different statistical approaches to investigate this issue, considering x2-test and Logit models. Our results show that data collection method may influence the response

Natalité et constitution des familles

[eng] The rhythm of families composition, in other words the time required between marriage and birth of first child, or between the following births, is a component of natality whose importance has scarcely been studied up-to-now. Therefore, from period to period, from social category to social category, the above-mentioned rhythm is liable to be affected by rather important variations, even if final descent is slightly affected. Families distribution, according to the number of their children, constitutes an explanatory though unsufficient factor of such differences. The variations of this rhythm, from period to period, produce substantial variations on natality, variations difficult to explain with the help of cyclical data. Nevertheless, it is liable establishing that the number of additional births, due to an acceleration of this rhythm, is responsible for the birth, in France, of an additional generation in the course of the period extending from 1940 to 1965. [spa] El ritmo al que se constituyen las familias, o en otras palabras, el tiempo transcurrido entre el matrimonio y el nacimiento del primer hijo, o entre los sucesivos nacimientos, es un componente de la natalidad, cuyo papel fué escasamente estudiado hasta la fecha. Así pues, de una época otra, de un grupo social a otro, ese ritmo puede presentar variaciones de suma consideración, incluso si la descendencia final cambia escasamente. La distribución de las familias según el número de sus hijos constituye un factor explicativo si bien insuficiente con relación a dichas variaciones. Las variaciones en el antecitado ritmo producen de una época a otra variaciones importantes relativas a natalidad, las que son difïcilmente apreciables mediante datos coyunturales. No obstante, es factible asentar que el número de nacimientos suplementarios, debidos a una acceleración de dicho ritmo, es responsable del nacimiento de una generación suplementaria en Francia en el transcurso del periodo que va de 1940 a 1945. [fre] Le rythme de constitution des familles, c'est-à-dire les délais entre mariage et première naissance, ou entre naissances successives, est une composante de la natalité dont le rôle a été peu étudié jusqu'ici. Or, d'une époque à l'autre, d'un groupe social à l'autre, ce rythme est susceptible de variations d'assez grande ampleur, même si la descendance finale ne change que peu. La répartition des familles selon leur nombre d'enfant est un facteur explicatif notable mais insuffisant de ces différences. Les variations de ce rythme d'une époque à l'autre produisent des variations substantielles sur la natalité, difficiles à apprécier à l'aide de données conjoncturelles. Cependant on peut établir que le nombre de naissances supplémentaires dues à une accélération de ce rythme est responsable de la naissance d'une génération supplémentaire en France, au cours de la période 1940-1965.