Gunnar Taraldsen

Gender differences in subjective well-being, self-esteem and psychosocial functioning in adolescents with symptoms of anxiety and depression: findings from the Nord-Trøndelag Health Study

Gender differences in the prevalence of symptoms of anxiety and depression during adolescence are well documented. However, little attention has been given to differences in subjective well-being, self-esteem and psychosocial functioning between boys and girls with symptoms of anxiety and depression. The aim of this study was to investigate gender differences in the associations between such symptoms and subjective well-being, self-esteem, school functioning and social relations in adolescents. Data were taken from a major population-based Norwegian study, the Nord-Trøndelag Health study (HUNT), in which 8984 (91% of all invited) adolescents, aged 13-19 years, completed an extensive self-report questionnaire. Although prevalence rates of symptoms of anxiety and depression were higher in girls than in boys, a significant interaction between gender and symptoms of anxiety and depression was found in respect of each of the following outcome variables: subjective well-being, self-esteem, academic problems, frequency of meeting friends and the feeling of not having enough friends. These interactions indicate that the associations between symptoms of anxiety and depression and lower subjective well-being and self-esteem, more academic problems in school and lower social functioning were stronger for boys than for girls. Our findings may contribute to an earlier assessment and more efficient treatment of male adolescent anxiety and depression.

Perinatal risk and psychiatric outcome in adolescents born preterm with very low birth weight or term small for gestational age.

Objective: To study perinatal risk factors for psychiatric symptoms in adolescents born preterm with very low birth weight or at term, but small for gestational age (GA). Method: Mental health was assessed in 65 adolescents born with very low birth weight (VLBW) (birth weight ≤1500 g), 59 born term small for GA (birth weight <10th centile) and 81 control adolescents using Schedule for Affective Disorders and Schizophrenia for School-Age Children, Childrens Global Assessment Scale, Autism Spectrum Screening Questionnaire, Attention-Deficit Hyperactivity Disorder-Rating Scale IV and Achenbach System of Empirically Based Assessment. Perinatal data included birth weight, GA, head circumference, Apgar scores, intraventricular hemorrhage, days in neonatal intensive care unit, and days on mechanical ventilation. Results: In the very low birth weight group, lower birth weight was associated with inattention (p < .01), psychiatric diagnoses, and reduced psychosocial function (p ≤ .05). Intraventricular hemorrhage increased the risk for a high inattention score (odds ratio = 7.5; 95% confidence intervals: 1.2–46.8). Lower Apgar score at 1 min was associated with a high Autism Spectrum Screening Questionnaire score and lower Apgar score at 5 min with a high internalizing score (p ≤ .05). In the subgroup born appropriate for GA, internalizing symptoms were also associated with lower GA. In the term small for GA group, perinatal events were not associated with psychiatric problems. In contrast, low socioeconomic status was associated with externalizing symptoms. Conclusion: Lower birth weight, shorter gestation, and intraventricular hemorrhage were risk factors for psychiatric problems in the very low birth weight group. Lower Apgar score increased the risk for autism spectrum symptoms and internalizing symptoms. Among adolescents born term small for GA, the main risk factor for psychiatric symptoms was low socioeconomic status.

Early prediction of cerebral palsy by computer-based video analysis of general movements: a feasibility study

Aim  The aim of this study was to investigate the predictive value of a computer‐based video analysis of the development of cerebral palsy (CP) in young infants.

Fiducial theory and optimal inference

It is shown that the fiducial distribution in a group model, or more generally a quasigroup model, determines the optimal equivariant frequentist inference procedures. The proof does not rely on existence of invariant measures, and generalizes results corresponding to the choice of the right Haar measure as a Bayesian prior. Classical and more recent examples show that fiducial arguments can be used to give good candidates for exact or approximate confidence distributions. It is here suggested that the fiducial algorithm can be considered as an alternative to the Bayesian algorithm for the construction of good frequentist inference procedures more generally.

Improper Priors Are Not Improper

It is well known that improper priors in Bayesian statistics may lead to proper posterior distributions and useful inference procedures. This motivates us to give an elementary introduction to a theoretical frame for statistics that includes improper priors. Axioms that allow improper priors are given by a relaxed version of Kolmogorov’s formulation of probability theory. The theory of conditional probability spaces formulated by Renyi is closely related, but the initial axioms and the motivation differ. One consequence of the axioms is a general Bayes theorem which gives proper posterior distributions, and furthermore, the theory also gives a convenient frame for formulation of non-Bayesian statistical models. The results are in particular relevant for the current usage of improper priors in Markov chain Monte Carlo methods, and for methods for simulation from conditional distributions given sufficient statistics. This theory gives an alternative to ad hoc arguments without an underlying theory, and removes apparent paradoxes. Readers who acknowledge the need for a theoretical basis for statistical inference including improper priors are urged to consider the theory of conditional probability spaces as presented here.

Instrument resolution and measurement accuracy

A procedure is presented to evaluate the expanded uncertainty of a quantity about which discretized measurement data are available. The method is based on conventional statistics and depends on the value of the experimental variance and the resolution. The suggested procedure is compared with a recently suggested procedure based on Bayesian statistics. The ISO Guide to the Expression of Uncertainity in Measurement (GUM) is discussed briefly. It is argued that both conventional and Bayesian statistics give a consistent interpretation of the GUM procedure, and the two approaches supplement each other: conventional statistics estimates the uncertainty of the measurement procedure, while Bayesian statistics gives the uncertainty of the measurand.

A note on reflection of spherical waves

In 1909 Sommerfeld gave an exact solution for the reflection of a spherical wave from a plane surface in terms of an oscillatory integral and also presented an asymptotic solution for the case where both source and receiver are at the boundary. Weyl (1919) presented an alternative solution and also an asymptotic solution for the case where the source is at the boundary. It is known that the general case is solved if a general solution for the case where the source is at the boundary is known. Here it is demonstrated that it is sufficient to have the general solution for the case where both source and receiver are at the boundary. This is mainly of theoretical interest, but may have practical applications. As an example it is demonstrated that Sommerfelds approximate solution gives Ingards (1951) approximate solution which is valid for arbitrary source and receiver heights.

Aspects of ground effect modeling

A recently published one-parameter ground model based on Darcys law is here generalized into a two-parameter model which depends on an effective flow resistivity and an effective layer depth. Extensive field measurements of the acoustic impedance of various ground types have been carried out for frequencies in the range from 200 Hz to 2.5 kHz. The model based on Darcys law gives an improved fit to the measurements compared to the Delany-Bazley model. It is, in addition, argued on purely theoretical grounds that the suggested model is preferable. In contrast to the Delany-Bazley model it corresponds to a proper causal time-domain model. This is particularly relevant for extrapolation of the models to lower frequencies and for the recently developed harmonized methods intended for use in the implementation of the European Union directive on the assessment and management of environmental noise. The harmonized methods include frequencies down to the 25 Hz third octave band and have the Delany-Bazley ground impedance model as the default choice. The arguments presented here suggest that this default choice should be replaced by the more physically based model from the law of Darcy.

Conditional probability and improper priors

ABSTRACT According to Jeffreys improper priors are needed to get the Bayesian machine up and running. This may be disputed, but usage of improper priors flourish. Arguments based on symmetry or information theoretic reference analysis can be most convincing in concrete cases. The foundations of statistics as usually formulated rely on the axioms of a probability space, or alternative information theoretic axioms that imply the axioms of a probability space. These axioms do not include improper laws, but this is typically ignored in papers that consider improper priors. The purpose of this paper is to present a mathematical theory that can be used as a foundation for statistics that include improper priors. This theory includes improper laws in the initial axioms and has in particular Bayes theorem as a consequence. Another consequence is that some of the usual calculation rules are modified. This is important in relation to common statistical practice which usually include improper priors, but tends to use unaltered calculation rules. In some cases, the results are valid, but in other cases inconsistencies may appear. The famous marginalization paradoxes exemplify this latter case. An alternative mathematical theory for the foundations of statistics can be formulated in terms of conditional probability spaces. In this case, the appearance of improper laws is a consequence of the theory. It is proved here that the resulting mathematical structures for the two theories are equivalent. The conclusion is that the choice of the first or the second formulation for the initial axioms can be considered a matter of personal preference. Readers that initially have concerns regarding improper priors can possibly be more open toward a formulation of the initial axioms in terms of conditional probabilities. The interpretation of an improper law is given by the corresponding conditional probabilities.

Estimation of aircraft angular coordinates using a directional-microphone array—An experimental studya)

Ground reflections cause problems when estimating the direction of arrival of aircraft noise. In traditional methods, based on the time differences between the microphones of a compact array, they may cause a significant loss of accuracy in the vertical direction. This study evaluates the use of first-order directional microphones, instead of omnidirectional, with the aim of reducing the amplitude of the reflected sound. Such a modification allows the problem to be treated as in free field conditions. Although further tests are needed for a complete evaluation of the method, the experimental results presented here show that under the particular conditions tested the vertical angle error is reduced ∼10° for both jet and propeller aircraft by selecting an appropriate directivity pattern. It is also shown that the final level of error depends on the vertical angle of arrival of the sound, and that the estimates of the horizontal angle of arrival are not influenced by the directivity pattern of the microphones nor by the reflective properties of the ground.