ingrdae

• Dæhlen, Ingrid & Hjort, Nils Lid (2025). Model robust hybrid likelihood. Journal of Statistical Planning and Inference. ISSN 0378-3758. 241. doi: 10.1016/j.jspi.2025.106327. Full text in Research Archive Show summary

  This article concerns hybrid combinations of empirical and parametric likelihood functions. Combining the two allows classical parametric likelihood to be crucially modified via the nonparametric counterpart, making possible model misspecification less problematic. Limit theory for the hybrid likelihood function is sorted out, also outside of the parametric model conditions. We prove a profiling result as well as limiting behaviour of the maximizer of the hybrid likelihood function. Our results allow for the presence of plug-in parameters in the hybrid and empirical likelihood framework. Furthermore, the variance and mean squared error of these estimators are studied, with recipes for their estimation. The latter is used to define a focused information criterion, which can be used to choose how the parametric and empirical part of the hybrid combination should be balanced. This allows for hybrid models to be fitted in a context driven way.

• Dreyer, Lars Willas; Rabault, Jean; Jensen, Atle; Dæhlen, Ingrid; Kristoffersen, Yngve & Breivik, Øyvind [Show all 7 contributors for this article] (2025). Direct in-situ observations of wave-induced floe collisions in the deeper Marginal Ice Zone. Cold Regions Science and Technology. ISSN 0165-232X. 240. doi: 10.1016/j.coldregions.2025.104642. Full text in Research Archive Show summary

  Ocean waves propagating through the Marginal Ice Zone (MIZ) and the pack ice are strongly attenuated. This attenuation is critical for protecting sea ice from energetic wave events that could otherwise lead to sea ice break-up and dislocation over large areas. Despite the importance of waves-in-ice attenuation, the exact physical mechanisms involved, and their relative importance, are still uncertain. Here we present direct in-situ measurements of floe-floe interactions under the influence of waves, including collisions between adjacent floes. The collision events we report are aligned with the incoming wave direction, and phase-locked to the wave signal, which indicates that the individual collisions we detect are wave-induced. The observations indicate a possible correlation between sudden increases in wave activity and the frequency of floe-floe collisions.

• Mathiesen, Liv; Nguyen, Tram Bich Michelle; Dæhlen, Ingrid; Mowe, Morten & Lea, Marianne (2024). Effect of integrated medicines management on quality of discharge medication information—a secondary endpoint in a randomized controlled trial. International Journal for Quality in Health Care. ISSN 1353-4505. 36(4), p. 1–8. doi: 10.1093/intqhc/mzae100. Full text in Research Archive Show summary

  Background High-quality discharge information is important to promote patient safety when patients are transferred from hospital to primary care. Patients with multiple long-term conditions are especially vulnerable to insufficient transfer of medication information, as they use many medications and have complex interactions with the healthcare services. The aim of this study was to investigate the effect of integrated medicines management provided to hospitalized multimorbid patients on the quality of the discharge medication information. Methods Multimorbid patients ≥18 years, using a minimum of four regular medications from a minimum of two therapeutic medication classes were recruited from the Internal Medicine ward, Oslo University Hospital, Norway, from August 2014 to March 2016 and randomly assigned, 1:1, to the intervention or control group. Intervention patients received integrated medicines management throughout the hospital stay. Control patients received standard care. This paper reports the results of a prespecified secondary endpoint analysis of the randomized controlled trial; the difference between the intervention and control group in the quality of discharge medication information. Results The analysis population comprised 384 patients. Integrated medicines management improved the discharge summary quality score of the medication information from 5.8 ± 1.5 to 8.6 ± 2.6 [mean difference 2.7, 95% confidence interval (CI) 2.3–3.2, P < .001]. In total, 171 intervention patients (89%) received a patient discharge information letter, compared to 66 control patients (35%), P < .001. The quality score of the medication information in the patient discharge information letter was improved from 6.0 ± 1.8 in the control group to 10.0 ± 1.3 in the intervention group (mean difference 4.0, 95% CI 3.6–4.4, P < .001). Conclusion Integrated medicines management delivered to multimorbid patients during a hospital stay improved the quality of the medication information in discharge summaries as well as patient discharge information letters and ensured that a discharge information letter in lay language was prepared for almost all patients who were involved in the management of their medications after discharge.

• Dæhlen, Ingrid; Hjort, Nils Lid & Haff, Ingrid Hobæk (2023). Accurate bias estimation with applications to focused model selection. Scandinavian Journal of Statistics. ISSN 0303-6898. p. 1–36. doi: 10.1111/sjos.12696. Full text in Research Archive Show summary

  Abstract We derive approximations to the bias and squared bias with errors of order where is the sample size. Our results hold for a large class of estimators, including quantiles, transformations of unbiased estimators, maximum likelihood estimators in (possibly) incorrectly specified models, and functions thereof. Furthermore, we use the approximations to derive estimators of the mean squared error (MSE) which are correct to order . Since the variance of many estimators is of order , this level of precision is needed for the MSE estimator to properly take the variance into account. We also formulate a new focused information criterion (FIC) for model selection based on the estimators of the squared bias. Lastly, we illustrate the methods on data containing the number of battle deaths in all major inter‐state wars between 1823 and the present day. The application illustrates the potentially large impact of using a less‐accurate estimator of the squared bias.

View all works in NVA

• Haug, Ola; Dæhlen, Ingrid; Aldrin, Magne Tommy & Aamodt, Randi Margrethe (2025). Environmental Risk Analysis of Nordre Follo Municipality's Sewage System Using Multivariate Statistical Analysis. Full text in Research Archive Show summary

  Environmental risk analyses of sewage systems shall be an integrated part of municipalities’ master plan for wastewater and storm water, as well as applications for permission of outlet to the State Governor. Such analyses are often performed in a manual and ad hoc, yet time-consuming way. Such simplified analyses typically include relatively few pipes, and the probability for different risk categories are often provided as crude estimates only. This approach does not at all harvest the full potential of connections and explanatory power that is contained in all the data available from the pipe system and the environment in combination. In this project, we develop a statistical framework that calculates environmental risk for 6200 sewage pipes based on data available for the municipality. The data set comprises three major sources: 1) Data from the professional VA wiring network system Gemini VA. This data set holds information on the geographical position of pipes, their age, material, diameter and slope, along with a history of maintenance and failures. 2) Data obtained from simulations of the sewage system in the hydraulic-hydrological software tool MIKE+. We perform model simulations for different precipitation events and prolonged dry weather periods. From these simulations we obtain for each pipe values of importance to pollution risk, for example: Overload, pressure, maximum and minimum water flow. 3) Data from environmental monitoring of the storm water system and urban streams in dry as well as wet weather. We measure six parameters: E.coli, total phosphorus, ortophosphate or total reactive phosphorus, total nitrogen, nitrate and ammonia in 400 manholes and stream monitoring locations. These data, called “weather pollution”, are assigned to the closest upstream sewage pipe, which also incorporates system information representative of the total upstream exposure. The analysis produces three main results: 1) Model simulation of a base risk value for each sewage pipe in dry weather or prolonged dry weather periods. The main risk is accumulation of sewage. 2) Calculation of a risk value for each pipe during overflow. The calculations are performed for different weather exposures represented via local precipitation intensity, duration and frequency (IDF) values for selected return periods. 3) Prediction of a “dry weather pollution” base risk value for pipes that have no monitored values, based on feeding their properties to the statistical framework. Most municipalities monitor their streams and lakes through the water areas, and many perform source tracking in the storm water system. If, in addition, a calibrated hydraulic-hydrological model of the sewage system is available, the suggested methodology can provide a more comprehensive analysis which is also more efficient.

• Dæhlen, Ingrid (2026). Vekting av boligprisestimat. Norsk Regnesentral. Full text in Research Archive
• Dæhlen, Ingrid & Løland, Anders (2025). Beregningsgrunnlag for lotterier. Norsk Regnesentral. Full text in Research Archive

View all works in NVA