Analytic urns

This article describes a purely analytic approach to urn models of the generalized or extended P\'olya-Eggenberger type, in the case of two types of balls and constant ``balance,'' that is, constant row sum. The treatment starts from a quasilinear first-order partial differential equation associated with a combinatorial renormalization of the model and bases itself on elementary conformal mapping arguments coupled with singularity analysis techniques. Probabilistic consequences in the case of ``subtractive'' urns are new representations for the probability distribution of the urn's composition at any time n, structural information on the shape of moments of all orders, estimates of the speed of convergence to the Gaussian limit and an explicit determination of the associated large deviation function. In the general case, analytic solutions involve Abelian integrals over the Fermat curve x^h+y^h=1. Several urn models, including a classical one associated with balanced trees (2-3 trees and fringe-balanced search trees) and related to a previous study of Panholzer and Prodinger, as well as all urns of balance 1 or 2 and a sporadic urn of balance 3, are shown to admit of explicit representations in terms of Weierstra\ss elliptic functions: these elliptic models appear precisely to correspond to regular tessellations of the Euclidean plane.Comment: Published at http://dx.doi.org/10.1214/009117905000000026 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

Pakilanpuiston suunnittelukiista : analyysi paikallisesta asukasaktivismista

Only abstract. Paper copies of master’s theses are listed in the Helka database (http://www.helsinki.fi/helka). Electronic copies of master’s theses are either available as open access or only on thesis terminals in the Helsinki University Library.Vain tiivistelmä. Sidottujen gradujen saatavuuden voit tarkistaa Helka-tietokannasta (http://www.helsinki.fi/helka). Digitaaliset gradut voivat olla luettavissa avoimesti verkossa tai rajoitetusti kirjaston opinnäytekioskeilla.Endast sammandrag. Inbundna avhandlingar kan sökas i Helka-databasen (http://www.helsinki.fi/helka). Elektroniska kopior av avhandlingar finns antingen öppet på nätet eller endast tillgängliga i bibliotekets avhandlingsterminaler.Tutkimuksen kohteena on Helsingin Pakilassa sijaitsevan Pakilanpuiston kaavamuutos, paikallisten asukasyhdistysten toiminta ja niiden intressit puiston kaavoituksen suhteen. Kaupunki kaavoitti alueelle uusia asuntoja ja kehitti puistoaluetta. Kaavoitusprosessi oli käynnissä vuoden 2005 tammikuusta lokakuuhun 2007, jolloin kaavamuutos hyväksyttiin kaupunginvaltuustossa. Tutkimuksessa esitellään myös alueen historiaa ja puistoalueen syntyä, käydään läpi kaavamuutosprosessi ja esitellään sen aiheuttamat muutokset alueelle. Tutkimuksen tarkoituksena on selvittää vaikuttaako tontin hallintamuoto asukasyhdistysten intresseihin Pakilanpuiston suunnittelua koskevassa keskustelussa, ovatko pakilalaiset asukasyhdistykset pääasiassa omaisuusarvoja puolustavia liikkeitä, minkälaisia keinoja niillä on vaikuttaa ja kuinka yhdistykset näkevät omat vaikutusmahdollisuutensa? Tutkimuksessa tarkasteltavat asukasyhdistykset ovat Pakila-seura ja Pakilan omakotiyhdistys. Tutkimusmenetelmänä on käytetty teemahastattelua ja niiden sisällön analyysia pohjaten vahvimmin John Emmeus Davisin teoreettiseen käsitteistöön asuinpaikasta syntyvään kollektiviseen toimintaan. Haastateltavat ovat Pakila-seuran ja Pakilan omakotiyhdistyksen aktiivijäseniä. Aineistona on lisäksi asukkaiden ja asukasyhdistysten lähettämät kirjelmät kaupungille kaavaehdotuksesta ja muistiot kaupunkisuunnitteluviraston järjestämistä keskustelutilaisuuksista. Tutkimuksen keskeisin teoreettinen pohja, John Emmeus Davisin teoria yhdistää marxilaista kollektiivisen toiminnan teoriaa neoweberiläisiin urbaaneja konflikteja ja asumista tutkiviin teorioihin. Teoriaosassa on lisäksi käyty läpi muun muassa Harvey Molotchin, Mike Davisin ja Mark Purcellin teoriaa ja käsitteistöä. Tutkimustulokset antavat kuvan, että tontin hallintamuodolla on vaikutusta asukasyhdistysten intresseihin kaavoituskiistassa. Pakila-seura, joka on Pakilan kaupunginosayhdistys ja Pakilan omakotiyhdistys, kaupungin vuokratonteille rakennettujen omakotitalojen asukasyhdistys ovat eri mieltä puiston suunnittelusta ja havaittavissa on myös alueen historian merkitys asukasyhdistysten vähäiselle yhteistyölle. Intressit eivät kuitenkaan ole pääsääntöisesti omaisuusarvoihin liittyviä. Tutkimustulokset näkevät yhtenä tärkeänä intressinä lähidemokratian vahvistamisen asuinalueella. Vaikuttamisen mahdollisuuksista yhdistykset antavat hieman ristiriitaisen kuvan johtuen todennäköisesti siitä, että Pakila-seura on ajanut suurempia hankkeita, joissa onnistumiset ovat harvemmassa ja omakotiyhdistys on keskittynyt enemmän itseään koskeviin pieniin kysymyksiin ja saavuttanut niissä onnistumisia

Sample Representation and Substantive Outcomes Using Web With and Without Incentives Compared to Telephone in an Election Survey

The objective of this article is to understand how the change of mode from telephone to web affects data quality in terms of sample representation and substantive variable bias. To this end, an experiment, consisting of a web survey with and without a prepaid incentive, was conducted alongside the telephone Swiss election survey. All three designs used identical questionnaires and probability samples drawn from a national register of individuals. First, our findings show that differences in completion rates mostly reflect different levels of coverage in the two modes. Second, incentives in the web survey strongly increase completion rates of all person groups, with the exception of people without Internet access or limited computer literacy. Third, we find voting behavior to be much closer to official figures in the web with the incentive version compared to the two other designs. However, this is partly due to the different sociodemographic compositions of the samples. Other substantive results suggest that the incentive version includes harder-to-reach respondents. Unit costs are much lower in the two web designs compared to the telephone, including when a relatively high incentive is used. We conclude that in countries with high Internet penetration rates such as Switzerland, web surveys are already likely to be highly competitive

Sequentially mixing modes in an election survey

In this paper, we analyze to what extent a sequential mixed mode survey, consisting of push-to-web, telephone and mail-paper modes, is able to improve representativeness in terms of socio-demographic variables and reduce bias in terms of voting behavior compared to a single mode survey. In addition, we study whether changes in mode lead to measurement error issues by focusing on income. We find that adding the telephone mode improves sample representation in terms of socio-demographic variables. Meanwhile, adding the paper mode does not show further improvements in this respect. However, adding the telephone, and in particular the paper mode, turn out to reduce bias in voting behavior when compared to official figures. As for measuring income, the web and the telephone mode perform similarly well. Finally, we find little evidence of measurement differences of income when the same respondents are interviewed first by web or telephone and subsequently by paper questionnaire

Undercoverage and Nonresponse in a List-sampled Telephone Election Survey

For landline telephone surveys in particular, undercoverage has been a growing problem. However, research regarding the relative contributions of socio-demographic bias and other composition effects is scarce. We propose to address this issue by analyzing an election survey which used a sample from a register-based sampling frame containing basic socio-demographic information and to which telephone numbers were subsequently matched. With respect to socio-demographic representation of the final sample, we find that difficult to match groups are also difficult to contact, while those who cooperate tend to have different characteristics. We find bias due to undercoverage to be of greater magnitude than noncontact bias, while noncooperation falls between the two. As for substantive variables, both additional efforts to match missing telephone numbers and the construction of better weights are successful in closing the gap between survey estimates of voting behavior and true values from the election results

Conditional distributions of frame variables and voting behaviour in probability‐based surveys and opt‐in panels

Probability-based web surveys are increasingly challenged by decreasing response rates and high costs. A cheap and convenient solution is to use ‘opt-in’ online panels, which are based on non-probability samples. However, the quality of the data such panels produce is subject to debate. To improve our understanding in this regard, especially in the Swiss context, we compare conditional distributions of sociodemographic variables and voting behaviour of two probability-based web surveys and three opt-in panels. Indeed, point estimates in opt-in panels are well studied, but bivariate relationships between variables, arguably more important for researchers in political science research, have received less attention. Our analysis has the advantage of most variables of interest being included in the sampling frame and thus the true values are known for each conditional distribution. Our results show a lack of consistency and reproducibility in the results from opt-in panels, which leads us to recommend care when using this type of data

Cost efficiency of incentives in mature probability-based online panels

Little is known about the trade-off between response rates and sample selection on the one hand and costs of different incentives on the other hand in mature online panel surveys. In wave 5 of the Panel Survey of the Swiss Election Study (Selects), a conditional CHF 20 (cash) is used for the politically least interested, while the remaining sample is randomized in two incentive groups: a conditional CHF 10 (cash) and a lottery (5x300 CHF). In the two experimental groups, there are only small differences regarding sample composition, and response rates are only slightly higher in the more expensive cash group. Given that costs are significantly lower in the lottery group, we conclude that it may be possible to save costs on incentives in a mature panel

Population toxicokinetics of benzene.

In assessing the distribution and metabolism of toxic compounds in the body, measurements are not always feasible for ethical or technical reasons. Computer modeling offers a reasonable alternative, but the variability and complexity of biological systems pose unique challenges in model building and adjustment. Recent tools from population pharmacokinetics, Bayesian statistical inference, and physiological modeling can be brought together to solve these problems. As an example, we modeled the distribution and metabolism of benzene in humans. We derive statistical distributions for the parameters of a physiological model of benzene, on the basis of existing data. The model adequately fits both prior physiological information and experimental data. An estimate of the relationship between benzene exposure (up to 10 ppm) and fraction metabolized in the bone marrow is obtained and is shown to be linear for the subjects studied. Our median population estimate for the fraction of benzene metabolized, independent of exposure levels, is 52% (90% confidence interval, 47-67%). At levels approaching occupational inhalation exposure (continuous 1 ppm exposure), the estimated quantity metabolized in the bone marrow ranges from 2 to 40 mg/day

Targeting Incentives in Mature Probability-based Online Panels

This paper complements earlier work about incentive effects in wave 5 of the Panel Survey of the Swiss Election Study (Selects) about the possibilities to decrease incentives for high estimated response propensity respondents. In the present paper, we study possibilities to decrease incentives in wave 6 for the complementary group, the low-propensity respondents. For high-propensity respondents, continuing an (expensive) conditional CHF 10 (cash) produced only slightly higher response rates and a similar sample composition compared with an (inexpensive) lottery (5 x 300 CHF) in wave 5. For high-propensity respondents, however, switching to the lottery produced an 8% points lower response rate compared with continuing a conditional CHF 20 (cash), although sample compositions were similar in wave 6. In addition, the more costly incentives from wave 5 (CHF 10 as opposed to the lottery) continued to produce slightly higher response rates for high-propensity respondents in wave 6 such that due to cumulated effects we need to relativize our statements about the small effects from wave 5