Pooling multiple imputations when the sample happens to be the population

Current pooling rules for multiply imputed data assume infinite populations. In some situations this assumption is not feasible as every unit in the population has been observed, potentially leading to over-covered population estimates. We simplify the existing pooling rules for situations where the sampling variance is not of interest. We compare these rules to the conventional pooling rules and demonstrate their use in a situation where there is no sampling variance. Using the standard pooling rules in situations where sampling variance should not be considered, leads to overestimation of the variance of the estimates of interest, especially when the amount of missingness is not very large. As a result, populations estimates are over-covered, which may lead to a loss of statistical power. We conclude that the theory of multiple imputation can be extended to the situation where the sample happens to be the population. The simplified pooling rules can be easily implemented to obtain valid inference in cases where we have observed essentially all units and in simulation studies addressing the missingness mechanism only.Comment: 6 pages, 1 figure, 1 tabl

Time integration methods for compressible flow

This thesis deals with implicit time integration methods for compressible flow\ud containing shock waves. Next to the question about a suitable implicit time\ud integration scheme for steady and unsteady flow the key questions concern\ud suitable accuracy criteria on the time step and a dynamical determination of\ud the accuracy time step during a simulation

Broken Stick Model for Irregular Longitudinal Data

Many longitudinal studies collect data that have irregular observation times, often requiring the application of linear mixed models with time-varying outcomes. This paper presents an alternative that splits the quantitative analysis into two steps. The first step converts irregularly observed data into a set of repeated measures through the broken stick model. The second step estimates the parameters of scientific interest from the repeated measurements at the subject level. The broken stick model approximates each subject's trajectory by a series of connected straight lines. The breakpoints, specified by the user, divide the time axis into consecutive intervals common to all subjects. Specification of the model requires just three variables: time, measurement and subject. The model is a special case of the linear mixed model, with time as a linear B-spline and subject as the grouping factor. The main assumptions are: Subjects are exchangeable, trajectories between consecutive breakpoints are straight, random effects follow a multivariate normal distribution, and unobserved data are missing at random. The R package brokenstick v2.5.0 offers tools to calculate, predict, impute and visualize broken stick estimates. The package supports two optimization methods, including options to constrain the variance-covariance matrix of the random effects. We demonstrate six applications of the model: Detection of critical periods, estimation of the time-to-time correlations, profile analysis, curve interpolation, multiple imputation and personalized prediction of future outcomes by curve matching

How Philip Morris manages disruptive regulations and what other industries can learn from them

In this thesis presented in a case study format, we will analyze what happened to Philip Morris and how they adapted their strategy in a disruptive regulatory environment. We will firstly dig into the history of what happened to Philip Morris when increased regulation put a halt to most marketing practices for all players in the tobacco industry and analyze their reactions and switches in strategy. We will then analyze other industries that are experiencing similar disruptions and assess what they can learn from what happened to PM. Methods used: We will analyze the tobacco industry through several interviews with industry experts to gain insider knowledge of how tobacco companies were dealing with such disruptions as well as analyzing closely the existing research. We will then do the same thing with the alcohol and food/drinks industry and see firstly how they overlap and what they can learn from PM. After analyzing closely the existing research and interviews it is safe to say that PM and other tobacco companies are masters in the art of managing disruptive change. They do so by investing heavily in lobbying, adapting constantly to new laws and find legal ways around such regulations and finally the active participation in reducing harm to smokers by heavy investments in reduced risk products. The alcohol and food/drinks industry are facing the same challenges today and can learn a lot from the strategies PM implemented to tackle disruptions.Nesta tese apresentada em formato de estudo de caso, analisaremos o que aconteceu com a Philip Morris e como ela adaptou sua estratégia. Em primeiro lugar, examinaremos a história do que aconteceu à Philip Morris quando o aumento da regulamentação interrompeu a maioria das práticas de marketing para todos os participantes da indústria do tabaco e analisaremos suas reações. Em seguida, analisaremos outros setores que estão passando por interrupções semelhantes e avaliaremos o que eles podem aprender com o que aconteceu com o PM. Métodos usados: Analisaremos a indústria do tabaco por meio de uma série de entrevistas com especialistas da indústria para obter conhecimento interno de como as empresas de tabaco estavam lidando com tais interrupções, bem como analisar de perto a pesquisa existente. Faremos então a mesma coisa com a indústria de álcool e alimentos/bebidas e veremos primeiro como eles se sobrepõem e o que podem aprender com o PM. Depois de analisar de perto as pesquisas e entrevistas existentes, é seguro dizer que a PM e outras empresas de tabaco são mestres na arte de gerenciar mudanças disruptivas. Eles fazem isso investindo pesadamente em lobby, adaptando-se constantemente a novas leis e encontrando formas legais de contornar essas regulamentações e, finalmente, participando ativamente na redução dos danos aos fumantes por meio de investimentos pesados em produtos de risco reduzido. A indústria de álcool e alimentos / bebidas está enfrentando os mesmos desafios hoje e pode aprender muito com as estratégias implementadas pela PM para enfrentar interrupções

Holland's own Kennedy Affair: conspiracy theories on the murder of Pim Fortuyn

"In this article the author will analyze the functioning of conspiracy dispositives from the bottom up and the nexus between conspiracy dispositives and security dispositives in the context of the political rise of right-wing populist Pim Fortuyn and the various conspiracy theories that arose after his murder and the effects these conspiracy theories had on Dutch politics and society. These counter-conspiracy theories revolved mainly around the suggestion that the political establishment was responsible for the murder or at least had turned a blind eye to it. The analysis shows that although a small Part of the conspiracy constructions can rightfully be understood as counter-conspiracy dispositives raised bottom up, in the majority of the cases a blurring can be noted between counter-conspiracy dispositives and conspiracy dispositives. This can be explained by the fact that - parts of - the seemingly counter-conspiracy dispositives were initiated, adopted and instrumentalized by actors from 'above': actors from the Dutch political and cultural establishment. In fact, an intra-elite competition was being battled out." (author's abstract

Naar een duurzame visserij. Het Productschap Vis als facilitator?

De afgelopen jaren is er veel discussie over de noodzakelijkheid van een nieuwe balans tussen ecologische en economische waarden. Breed wordt erkend dat het tijd is om te zoeken naar nieuwe verhoudingen tussen deze, vaak strijdige, belangen (zie Weggeman, 2003). De visserij is één van de sectoren waarin deze discussie wordt gevoerd. Onder aanvoering van haar brancheorganisaties probeert de visserij de ‘vergroening’ van het visserijbeleid in een voor haar wenselijke richting te sturen. Het ministerie van Landbouw en de Europese Commissie trachten daarentegen de sector te stimuleren en zonodig te dwingen meer duurzame vormen van visserij te ontwikkelen. Het Productschap Vis heeft een lastige positie in deze discussie. Enerzijds behoort het de belangen van de sector te verdedigen, anderzijds moet het schap ook het algemeen belang behartigen. Het moet voortdurend inschatten wat het wel en niet kan, gegeven de opvattingen in de sector over wederzijdse domeinen en geëigende praktijken, ofwel de geldende institutionele verhoudingen. In dit artikel wil ik ingaan op de vraag hoe het schap invulling geeft aan zijn positie binnen deze spanningsvolle institutionele structuren