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- Hudson, Lawrence N, et al.
(författare)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 4. |
- Baranowska-Rataj, Anna, 1980-, et al.
(författare)
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Does the number of siblings affect health in midlife? : Evidence from the Swedish Prescribed Drug Register
- 2016
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Ingår i: Demographic Research. - Max Planck Institute for Demographic Research. - 1435-9871. ; 35, s. 1259-1302
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Tidskriftsartikel (refereegranskat)abstract
- Background: In many societies, growing up in a large family is associated with receiving less parental time, attention, and financial support. As a result, children with a large number of siblings may have worse physical and mental health outcomes than children with fewer siblings.Objective: Our objective is to examine the long-term causal effects of sibship size on physical and mental health in modern Sweden.Methods: We employ longitudinal data covering the entire Swedish population from the Multigenerational Register and the Medical Birth Register. This data includes information on family size and on potential confounders such as parental background. We use the Prescribed Drug Register to identify the medicines that have been prescribed and dispensed. We use instrumental variable models with multiple births as instruments to examine the causal effects of family size on the health outcomes of children, as measured by receiving medicines at age 45.Results: Our results indicate that in Sweden, growing up in a large family does not have a detrimental effect on physical and mental health in midlife.Contribution: We provide a systematic overview of the health-related implications of growing up in a large family. We adopt a research design that gives us the opportunity to make causal inferences about the long-term effects of family size. Moreover, our paper provides evidence on the links between family size and health outcomes in the context of a developed country that implements policies oriented towards reducing social inequalities in health and other living conditions.
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| 5. |
- Barban, Nicola, et al.
(författare)
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Causal Effects of the Timing of Life-course Events : Age at Retirement and Subsequent Health
- 2020
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Ingår i: Sociological Methods & Research. - : Sage Publications. - 0049-1241 .- 1552-8294. ; 49:1, s. 216-249
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we combine the extensive literature on the analysis of life-course trajectories as sequences with the literature on causal inference and propose a new matching approach to investigate the causal effect of the timing of life-course events on subsequent outcomes. Our matching approach takes into account pre-event confounders that are both time-independent and time-dependent as well as life-course trajectories. After matching, treated and control individuals can be compared using standard statistical tests or regression models. We apply our approach to the study of the consequences of the age at retirement on subsequent health outcomes, using a unique data set from Swedish administrative registers. Once selectivity in the timing of retirement is taken into account, effects on hospitalization are small, while early retirement has negative effects on survival. Our approach also allows for heterogeneous treatment effects. We show that the effects of early retirement differ according to preretirement income, with higher income individuals tending to benefit from early retirement, while the opposite is true for individuals with lower income.
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| 8. |
- Broström, Göran, et al.
(författare)
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Att läsa i Umeå är ett bra val
- 2005
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Ingår i: Västerbottens-Kuriren. ; :9 december, s. 4-
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 9. |
- Bränberg, Kenny, 1956-
(författare)
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Observed score equating with covariates
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In test score equating the focus is on the problem of finding the relationship between the scales of different test forms. This can be done only if data are collected in such a way that the effect of differences in ability between groups taking different test forms can be separated from the effect of differences in test form difficulty. In standard equating procedures this problem has been solved by using common examinees or common items. With common examinees, as in the equivalent groups design, the single group design, and the counterbalanced design, the examinees taking the test forms are either exactly the same, i.e., each examinee takes both test forms, or random samples from the same population. Common items (anchor items) are usually used when the samples taking the different test forms are assumed to come from different populations. The thesis consists of four papers and the main theme in three of these papers is the use of covariates, i.e., background variables correlated with the test scores, in observed score equating. We show how covariates can be used to adjust for systematic differences between samples in a non-equivalent groups design when there are no anchor items. We also show how covariates can be used to decrease the equating error in an equivalent groups design or in a non-equivalent groups design. The first paper, Paper I, is the only paper where the focus is on something else than the incorporation of covariates in equating. The paper is an introduction to test score equating, and the author's thoughts on the foundation of test score equating. There are a number of different definitions of test score equating in the literature. Some of these definitions are presented and the similarities and differences between them are discussed. An attempt is also made to clarify the connection between the definitions and the most commonly used equating functions. In Paper II a model is proposed for observed score linear equating with background variables. The idea presented in the paper is to adjust for systematic differences in ability between groups in a non-equivalent groups design by using information from background variables correlated with the observed test scores. It is assumed that conditional on the background variables the two samples can be seen as random samples from the same population. The background variables are used to explain the systematic differences in ability between the populations. The proposed model consists of a linear regression model connecting the observed scores with the background variables and a linear equating function connecting observed scores on one test forms to observed scores on the other test form. Maximum likelihood estimators of the model parameters are derived, using an assumption of normally distributed test scores, and data from two administrations of the Swedish Scholastic Assessment Test are used to illustrate the use of the model. In Paper III we use the model presented in Paper II with two different data collection designs: the non-equivalent groups design (with and without anchor items) and the equivalent groups design. Simulated data are used to examine the effect - in terms of bias, variance and mean squared error - on the estimators, of including covariates. With the equivalent groups design the results show that using covariates can increase the accuracy of the equating. With the non-equivalent groups design the results show that using an anchor test together with covariates is the most efficient way of reducing the mean squared error of the estimators. Furthermore, with no anchor test, the background variables can be used to adjust for the systematic differences between the populations and produce unbiased estimators of the equating relationship, provided that the “right” variables are used, i.e., the variables explaining those differences. In Paper IV we explore the idea of using covariates as a substitute for an anchor test with a non-equivalent groups design in the framework of Kernel Equating. Kernel Equating can be seen as a method including five different steps: presmoothing, estimation of score probabilities, continuization, equating, and calculating the standard error of equating. For each of these steps we give the theoretical results when observations on covariates are used as a substitute for scores on an anchor test. It is shown that we can use the method developed for Post-Stratification Equating in the non-equivalent groups with anchor test design, but with observations on the covariates instead of scores on an anchor test. The method is illustrated using data from the Swedish Scholastic Assessment Test.
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| 10. |
- Brännäs, Kurt, et al.
(författare)
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Generalized method of moment and indirect estimation of the ARasMA model
- 1998
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Ingår i: Computational statistics (Zeitschrift). - 0943-4062 .- 1613-9658. ; 13:4, s. 485-494
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Tidskriftsartikel (refereegranskat)abstract
- Estimation in nonlinear time series models has mainly been performed by least squares or maximum likelihood (ML) methods. The paper suggests and studies the performance of generalized method of moments (GMM) and indirect estimators for the autoregressive asymmetric moving average model. Both approaches are easy to implement and perform well numerically. In a Monte Carlo study it is found that the MSE properties of GMM are close to those of ML. The indirect estimator performs poorly in this respect. On the other hand, the three estimation techniques lead to fairly similar power functions for a linearity test.
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