Simple and statistically sound recommendations for analysing physical theories.

Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.

The Change in the Content of Nutrients in Diets Eliminating Products of Animal Origin in Comparison to a Regular Diet from the Area of Middle-Eastern Europe.

INTRODUCTION: The diet of Poles became similar to the western style of nutrition. It is rich in saturated fats, it contains significant quantities of salt, and has very low fruit and vegetable content. On the other hand, introducing an incorrectly planned diet that eliminates animal products may be associated with the risk of deficiencies of certain vitamins and minerals. Taking into account the regular diet of Poles, a properly balanced vegetarian menu may be a better and safer choice for the proper functioning of the organism. AIM: The analysis of the content of individual types of vegetarian diets and a comparison with the menus of the regular diet of the Polish population. MATERIALS AND METHODS: 70 menus were subjected to a quantitative analysis, 10 menus for each 7 type of diet eliminating products of animal origin and regular diets without elimination. The caloricity of the designed diets was ±2000 kcal. The quantitative evaluation of the menus was performed using the Dieta 6d dietary program. Statistical significance was established at p ≤ 0.05. RESULTS: It was observed that the regular diet of Poles (RD) featured the highest content of total fats, as well as saturated acids and cholesterol. The VEGAN diet was characterized by the lowest total protein content and the lack of wholesome protein and cholesterol. RD was characterized by the lowest average content of dietary fiber. The highest content of saccharose was observed in RD. Sodium content in RD significantly exceeded the recommended daily norm. RD featured insufficient content of the following minerals and vitamins: potassium, calcium, magnesium, iodine, Vitamin E, Vitamin C, folates, and Vitamin D. The norm for calcium has not been fulfilled also in milk-free and vegan diets. All of the analyzed diets lacked proper amounts of iodine and Vitamin D. The highest content of polyunsaturated fatty acids was observed in the VEGAN diet. The periodic elimination of meat and fatty dairy products should be included in the treatment of the metabolic syndrome, hypertensions, hyperlipidemia, obesity, and type 2 diabetes. CONCLUSIONS: The regular diet of Poles turned out to be more dangerous for health in terms of deficiencies than properly balanced diets eliminating products of animal origin.

Scaling of human behavior during portal browsing.

We investigated flows of visitors migrating between different portal subpages. Two various portals were studied as weighted networks where nodes are portal subpages and edge weights are numbers of user transitions. Such networks differ from networks of portal subpages connected by hyperlinks prepared by portal designers. Distributions of link weights, node strengths, and times spent by visitors at one subpage follow power laws over several decades for data collected during two different days and for weekly data. The distribution of numbers P(z) of unique subpages visited during one session is exponential and there is a square-root dependence between the total number of transitions n during a single visit and the average z . A model of portal surfing is developed where the browsing process corresponds to a self-attracting walk on the weighted network with a short memory. Results of numerical simulation are in agreement with weekly and daily portal data, and our analytical approach fits empirical data in the center part of scaling regime.