Jakob Bergman

Lund University | LU · Department of Statistics

We introduce a maximum likelihood ratio test to test if a specific proportion is the greatest in a multinomial situation with a single measurement. The test is based on partitioning the parameter space and utilising logratio transformations.

A large number of polls on party preferences are published today. In order to obtain an estimate of the changes in political opinion, the polls may be combined into a poll of polls. We discuss a method for combining polls using the fact that they are compositions and respecting the properties of the compositional sample space (the simplex). The met...

We present the first results of an experiment which is aimed at ultimately producing recommendations for analysing archaeologic ceramics specimens using handheld XRF analysis devices. In this experiment we study the effects of different measurement durations, different number of measured points and three different types of surface treatments (break...

We consider the problem of describing the correlation between two compositions. Using a bicompositional Dirichlet distribution, we calculate a joint correlation coefficient, based on the concept of information gain, between two compositions. Numerical values of the joint correlation coefficient are calculated for compositions of two and three compo...

The composition of the labour force is an important economic factor for a country. Often the changes in proportions of different groups are of interest.I this paper we study a monthly compositional time series from the Swedish LabourForce Survey from 1994 to 2005. Three models are studied: the ILR-transformed series,the ILR-transformation of the co...

Stable isotope analysis (N and C) of fossil cereal grains is regularly explored as a means of obtaining insights to past crop growing conditions and agricultural practices. In this study, we assessed how several growth conditions can affect δ 15 N and δ 13 C values of modern cereal grain with the aim to help understand isotopic values from ancient...

Measurements of archaeological cereal grains has the potential to improve interpretations of archaeobotanical assemblages and to address a broad range of research questions related to agricultural practices in the past. However, understanding the role of the many factors that can influence the morphometrics of cereal grains is of importance to vali...

In recruitment, promotion, admission, and other forms of wealth and power apportion, an evaluator typically ranks a set of candidates in terms of their competence. If the evaluator is prejudiced, the resulting ranking will misrepresent the candidates’ actual rankings. This constitutes not only a moral and a practical problem, but also an epistemolo...

This study uses crop stable nitrogen isotope analysis of charred grain to explore manuring practices in arable production at the affluent regional center Uppåkra and a set of smaller surrounding sites, dating to the first millennium AD in southern Sweden. The isotopic analysis focuses on hulled barley, the principle crop in the Scandinavian Iron Ag...

Supplementary results. Details of precision and accuracy, and calibration data (δ15N and %N). (DOCX)

Dataset of archaeological grain from study area. δ15N values, sample information, metric data and archaeological accession information for all analyzed grain. (XLSX)

Dataset of modern grain from field experiment. δ15N values, sample information and metric data for all analyzed grain. (XLSX)

When different polling organisations conduct political party preference polls at different times, different parties might be reported. If the estimated voter shares of these polls are combined into a time series we obtain a compositional time series, but with varying number of parts, thus prohibiting the use of standard compositional time series an...

Den 20 augusti 2015 hävdade dagstidningen Metro att Sverigedemokraterna var Sveriges största parti. Detta baserade man på att partiet blivit det största i en opinions-undersökning av företaget YouGov. Men hur kan man testa påståendet att en specifik andel är den största? Vi tar vår utgångspunkt i andelarnas speciella parameterrum simplex och dess i...

We present the first results of an experiment which is aimed at ultimately producing recommendations for analysing archaeologic ceramics specimens using hand held XRF analysis devices. In the experiment we study the effects of different measurement durations, different number of measured points, and three different types of surface treatments (brea...

A composition is a vector of positive components summing to a constant. The sample space of a composition is the simplex, and the sample space of two compositions, a bicomposition, is a Cartesian product of two simplices. We present a way of generating random variates from a bicompositional Dirichlet distribution defined on the Cartesian product of...

Cleveland (1979) is usually credited with the introduction of the locally weighted regression, Loess. The concept was further developed by Cleveland and Devlin (1988). The general idea is that for an arbitrary number of explanatory data points x i the value of a dependent variable is estimate y i . Thê y i is the fitted value from a dth degree poly...

A composition is a vector of positive components summing to a constant, usually taken to be 1. Hitherto the research on compositional correlation has mainly focused on the correlation between the components of composition. This thesis is concerned with modelling the correlation between two compositions. We introduce a generalization of the Dirichl...