Residual-based test for Nonlinear Cointegration with application in PPPs

Nested by linear cointegration first provided in Granger (1981), the definition of nonlinear cointegration is presented in this paper. Sequentially, a nonlinear cointegrated economic system is introduced. What we mainly study is testing no nonlinear cointegration against nonlinear cointegration by residual-based test, which is ready for detecting stochastic trend in nonlinear autoregression models. We construct cointegrating regression along with smooth transition components from smooth transition autoregression model. Some properties are analyzed and discussed during the estimation procedure for cointegrating regression, including description of transition variable. Autoregression of order one is considered as the model of estimated residuals for residual-based test, from which the teststatistic is obtained. Critical values and asymptotic distribution of the test statistic that we request for different cointegrating regressions with different sample sizes are derived based on Monte Carlo simulation. The proposed theoretical methods and models are illustrated by an empirical example, comparing the results with linear cointegration application in Hamilton (1994). It is concluded that there exists nonlinear cointegration in our system in the final results.

Kvinnors erfarenhet av postoperativ smärta och smärtlindring efter kejsarsnitt

Background: Many women experience high levels of pain after caesarean birth. Adequate postoperative pain treatment is important for the mother to be able to breastfeed, take care of the infant and experience a positive birth. Objective: The overall aim is to study women’s experience of postoperative pain and pain relief after caesarean birth. Method: A quantitative retrospective survey. Data were collected thru a questionnaire from Centralsjukhuset in Karlstad and Falu Larsarett in Sweden. Ninety-eight women participated in the study. Data was analysed with descriptive and comparative statistic. Result: Eighty percent of the women rated the pain with VAS = 4 during the first 24 hours post operative. Those who had to undergo acute caesarean birth rated significant higher levels of pain compared with those who had undergone planned caesarean birth. Despite high level of pain the women were satisfied with the pain relief they received. Both the ability to breastfeed and take care of the infant were affected by pain the first 24 hours post operative. Those who had undergone emergency caesarean birth experienced in greater extend the birth in a negative way. Conclusion: Postoperative pain affects the women’s ability to breastfeed and takes care of here infant. Adequate pain management is therefore important. The women who had to undergo emergency caesarean birth have a more negative birth experience. Midwifes have an important role to inform and support the women in processing here experience.

On statistical bounds of heuristic solutions to location problems

Solutions to combinatorial optimization problems, such as problems of locating facilities, frequently rely on heuristics to minimize the objective function. The optimum is sought iteratively and a criterion is needed to decide when the procedure (almost) attains it. Pre-setting the number of iterations dominates in OR applications, which implies that the quality of the solution cannot be ascertained. A small, almost dormant, branch of the literature suggests using statistical principles to estimate the minimum and its bounds as a tool to decide upon stopping and evaluating the quality of the solution. In this paper we examine the functioning of statistical bounds obtained from four different estimators by using simulated annealing on p-median test problems taken from Beasley’s OR-library. We find the Weibull estimator and the 2nd order Jackknife estimator preferable and the requirement of sample size to be about 10 being much less than the current recommendation. However, reliable statistical bounds are found to depend critically on a sample of heuristic solutions of high quality and we give a simple statistic useful for checking the quality. We end the paper with an illustration on using statistical bounds in a problem of locating some 70 distribution centers of the Swedish Post in one Swedish region. 

Testing for Seasonal Unit Roots when Residuals Contain Serial Correlations under HEGY Test Framework

This paper introduces a corrected test statistic for testing seasonal unit roots when residuals contain serial correlations, based on the HEGY test proposed by Hylleberg,Engle, Granger and Yoo (1990). The serial correlations in the residuals of test regressionare accommodated by making corrections to the commonly used HEGY t statistics. Theasymptotic distributions of the corrected t statistics are free from nuisance parameters.The size and power properties of the corrected statistics for quarterly and montly data are investigated. Based on our simulations, the corrected statistics for monthly data havemore power compared with the commonly used HEGY test statistics, but they also have size distortions when there are strong negative seasonal correlations in the residuals.

Kundernas behov i butiksmiljöer : Skillnaderna mellan handlares och kunders uppfattning av kundernas behov i klädbutiker

Konkurrensen inom detaljhandeln blir allt hårdare, både från andra butiker men även från e-handeln, vilket sätter press på fysiska butiker att ha nöjda kunder som fortsätter handla i butiken. Ett tillvägagångssätt för att möta den hårdnande konkurrensen är att ha en butiksmiljö s.k. servicescape som är utformad efter kundernas behov, vilket dock förutsätter att handlarna vet vilka behov sina kunder har. Har handlarna en felaktig uppfattning om kundernas behov föreligger det ett gap som minskar chansen att kunderna blir nöjda och därmed butikens konkurrenskraft. En avgränsning gjordes till klädbutiker, då klädbutiker är bland de butikstyper som är mest konkurrensutsatt. Syftet med uppsatsen var att kartlägga hur kundernas behov överensstämmer eller skiljer sig från handlarnas uppfattning om deras behov. För att uppfylla syftet tillämpades en kvalitativ metod men med en statistisk bearbetning dvs. en kvantitativ bearbetning då resultatet redovisades med hjälp av frekvenser och värden på en skala. Datainsamlingsverktyget som användes var enkäter och utformades efter de tio faktorerna som sammanställdes i den teoretiska referensramen. Enkäterna delades ut till både kunder och handlare i Borlänges stadskärna och Faluns stadskärna. Resultatet av uppsatsen visade att det för faktorerna ljus (4,2), trängsel (4.5) (4.6), Ljud (4.7), toaletter (4.9), (4.10) finns en skillnad ett s.k. gap mellan handlarnas uppfattning om kundernas behov och vad kundernas behov egentligen är. Det framkom även att handlarna ansåg att kunderna har större behov av att faktorerna rent & städat (4.3), (4.4) in & utgångar (4.8) är tillfredsställande än vad kunderna egentligen har. Det framkom precis som behandlades i den teoretiska referensramen att kundernas behov tenderar att variera utifrån deras demografiska faktorer ålder och kön. Om handlarna har en låg, medel eller hög prisnivå påverkade även det hur viktigt det är för kunderna att faktorerna är tillfredsställande. Slutsatsen som författarna identifierade var att det föreligger ett gap mellan handlarnas uppfattning om kundernas behov och vad kunderna anser att deras behov är gällande flera av faktorerna. Detta är dock något som kunderna säger vilket inte behöver stämma överrens med hur de verkligen tycker. Det är dock svårt att urskilja något mönster gällande gapen utan det är nästan enbart tendenser man kan urskilja, vilket gör att varje faktor bör analyseras individuellt.

Ekologiska kläder : En studie om varför konsumtionen av ekologiska kläder haft en svag ökning sett utifrån konsumenternas perspektiv

Syftet med denna studie är att förklara varför konsumtionen av ekologiska kläder haft en svag ökning sett utifrån konsumenternas perspektiv. För att kunna besvara syftet har en kvantitativ metod legat till grund för denna studie. Data har samlats in med hjälp av enkäter för att undersöka om det föreligger något samband bland konsumenter. För att kunna presentera ett mer djupgående resultat har den kvantitativa metoden kombinerats med en kvalitativ metod vid analys av data. Teorin i denna studie har använts som utgångspunkt för att bättre förstå konsumenternas köpbeteende samt betydelsen av varumärken. Studiens empiri består av den data som samlats in genom enkäter. I studies analys och diskussion har teorierna sedan tillämpats på den data som enkäterna genererat för att öka resultatets trovärdighet. I denna studie framkom att kvinnliga konsumenter i åldern 20-35 har låg kunskap om de konventionella klädernas påverkan på miljö och individ. Konsumenternas personliga behov värderas högre än socialt ansvarstagande och det som prioriteras högst vid köp av kläder är pris, design och kvalitet. Utbudet av ekologiska kläder är inte tillräckligt stort och de kläder som finns tillgängliga på marknaden saknar varumärkesimage och förknippas ofta med basplagg.

Modelling dominance in a flexible intercross analysis

The aim of this paper is to develop a flexible model for analysis of quantitative trait loci (QTL) in outbred line crosses, which includes both additive and dominance effects. Our flexible intercross analysis (FIA) model accounts for QTL that are not fixed within founder lines and is based on the variance component framework. Genome scans with FIA are performed using a score statistic, which does not require variance component estimation. RESULTS: Simulations of a pedigree with 800 F2 individuals showed that the power of FIA including both additive and dominance effects was almost 50% for a QTL with equal allele frequencies in both lines with complete dominance and a moderate effect, whereas the power of a traditional regression model was equal to the chosen significance value of 5%. The power of FIA without dominance effects included in the model was close to those obtained for FIA with dominance for all simulated cases except for QTL with overdominant effects. A genome-wide linkage analysis of experimental data from an F2 intercross between Red Jungle Fowl and White Leghorn was performed with both additive and dominance effects included in FIA. The score values for chicken body weight at 200 days of age were similar to those obtained in FIA analysis without dominance. CONCLUSION: We have extended FIA to include QTL dominance effects. The power of FIA was superior, or similar, to standard regression methods for QTL effects with dominance. The difference in power for FIA with or without dominance is expected to be small as long as the QTL effects are not overdominant. We suggest that FIA with only additive effects should be the standard model to be used, especially since it is more computationally efficient.

Large-scale metabolomic profiling identifies novel biomarkers for incident coronary heart disease

Analyses of circulating metabolites in large prospective epidemiological studies could lead to improved prediction and better biological understanding of coronary heart disease (CHD). We performed a mass spectrometry-based non-targeted metabolomics study for association with incident CHD events in 1,028 individuals (131 events; 10 y. median follow-up) with validation in 1,670 individuals (282 events; 3.9 y. median follow-up). Four metabolites were replicated and independent of main cardiovascular risk factors [lysophosphatidylcholine 18∶1 (hazard ratio [HR] per standard deviation [SD] increment = 0.77, P-value<0.001), lysophosphatidylcholine 18∶2 (HR = 0.81, P-value<0.001), monoglyceride 18∶2 (MG 18∶2; HR = 1.18, P-value = 0.011) and sphingomyelin 28∶1 (HR = 0.85, P-value = 0.015)]. Together they contributed to moderate improvements in discrimination and re-classification in addition to traditional risk factors (C-statistic: 0.76 vs. 0.75; NRI: 9.2%). MG 18∶2 was associated with CHD independently of triglycerides. Lysophosphatidylcholines were negatively associated with body mass index, C-reactive protein and with less evidence of subclinical cardiovascular disease in additional 970 participants; a reverse pattern was observed for MG 18∶2. MG 18∶2 showed an enrichment (P-value = 0.002) of significant associations with CHD-associated SNPs (P-value = 1.2×10-7 for association with rs964184 in the ZNF259/APOA5 region) and a weak, but positive causal effect (odds ratio = 1.05 per SD increment in MG 18∶2, P-value = 0.05) on CHD, as suggested by Mendelian randomization analysis. In conclusion, we identified four lipid-related metabolites with evidence for clinical utility, as well as a causal role in CHD development.