Conjoint analysis is a popular experimental design used to measure multidimensional preferences. Many researchers focus on estimating the average marginal effects of each factor while averaging over the other factors. Although this allows for straightforward design-based estimation, the results critically depend on the ways in which factors interact with one another. An alternative model-based approach can compute various quantities of interest, but requires correct model specifications, a challenging task for conjoint analysis with many factors. We propose a new hypothesis testing approach based on the conditional randomization test (CRT) to answer the most fundamental question of conjoint analysis: Does a factor of interest matter in any way given the other factors? Although it only provides a formal test of these binary questions, the CRT is solely based on the randomization of factors, and hence requires no modeling assumption. This means that the CRT can provide a powerful and assumption-free statistical test by enabling the use of any test statistic, including those based on complex machine learning algorithms. We also show how to test commonly used regularity assumptions. Finally, we apply the proposed methodology to conjoint analysis of immigration preferences. An open-source software package is available for implementing the proposed methodology. The proposed methodology is implemented via an open-source software R package CRTConjoint, available through the Comprehensive R Archive Network https://cran.r-project.org/web/packages/CRTConjoint/index.html.

A field experiment with the 35–1 fractional factorial design and five factors (k = 5) at three levels (s = 3) was performed in 2007–2010 at the Agricultural Experiment Station in Bałcyny, north-eastern (NE) Poland. The results of the experiment carried out under the agro-ecological conditions of NE Poland confirmed the high yield potential of common wheat and satisfactory yield potential of spelt and durum wheat. On average, durum wheat and spelt yields were 2.14 and 2.55 t/ha lower, respectively, than common wheat yields. Sowing date was not correlated with the yields of analysed Triticum species. Seed rate (350, 450 and 550 seeds/m2) had no significant influence on the grain yield of winter cultivars of common wheat, durum wheat and spelt. Common wheat cv. Oliwin and durum wheat cv. Komnata were characterized by the highest yields in response to nitrogen (N) fertilizer rates calculated based on the Nmin content of soil. An increase in the spring fertilizer rate by 40 kg N/ha in excess of the balanced N rate was not justified because it did not induce a further increase in the grain yield of common wheat and durum wheat. The grain yield of spelt cv. Schwabenkorn continued to increase in response to the highest rate of N fertilizer in spring (40 kg N/ha higher than the optimal rate). Intensified fungicide treatments improved grain yield in all Triticum species.

Randomized controlled trials (RCTs), typically, randomize participants to one of two intervention groups. It has been shown, however, that about 25% of RCTs published in the scientific literature randomize participants to three or more treatment groups. These studies are called ‘multi-arm’ trials: there may be, for instance, two or more experimental intervention groups with a common control group, or two control intervention groups such as a placebo group and a standard treatment group. A special case of multi-arm studies are factorial trials, which address two or more intervention comparisons carried out simultaneously, using four or more intervention groups.

La modélisation et la fabrication des ballons pressurisés stratosphériques longue durée à usage scientifique sont un défi pour le CNES. Ils sont constitués de plusieurs fuseaux en tri-couches PET/PA/PET d'épaisseur 50 µm, assemblés entre eux par des rubans adhésifs en PET de 23 µm d'épaisseur. À ce jour, un problème majeur apparaît lors des missions de vol, se traduisant pour certains ballons par une destruction prématurée. Ce travail porte sur l'étude du comportement mécanique des ballons pressurisés stratosphériques et plus particulièrement sur les assemblages des films polymères constituant le ballon. Dans un premier temps, une campagne d'essais de nanoindentation nous permet d'identifier les propriétés élastiques des matériaux après assemblage, et ce pour deux températures de vol du ballon. Dans un second temps, nous modélisons un assemblage nominal en approche 2D puis 3D. Plus particulièrement, un exemple d'application de la technique de submodeling est présenté à partir de la modélisation d'un défaut de la jonction. Enfin, à l'aide de la méthode des plans d'expériences et de simulations éléments-finis, nous étudions l'influence des paramètres de conception sur la tenue mécanique d'un assemblage type.