Estimation of relative survival has become the first and the most basic step when reporting cancer survival statistics. Standard estimators are in routine use by all cancer registries. However, it has been recently noted that these estimators do not provide information on cancer mortality that is independent of the national general population mortality. Thus they are not suitable for comparison between countries. Furthermore, the commonly used interpretation ofthe relative survival curve is vague and misleading. The present article attempts to remedy these basic problems. The population quantities of the traditional estimators are carefully described and their interpretation discussed. We then propose a new estimator of net survival probability that enables the desired comparability between countries. The new estimator requires no modeling and is accompanied with a straightforward variance estimate. The methods are described on real as well as simulated data.
COBISS.SI-ID: 28569561
Evaluating the performance of institutions with different resources is not easy, any citation distribution comparisons are strongly affected by the differences in the number of articles published. The paper introduces a methodfor comparing citation distributions of research groups that differ in size. The citation distribution of a larger group is reduced by a certain factor and compared with the original distribution of a smaller group. Expected values and tolerance intervals of the reduced set of citations are calculated. A comparison of both distributions can be conveniently viewed in agraph. The size-independent reduced Hirsch index - a function of reducing factor that allows the comparison of groups within a scientific field - is calculated in the same way. The method can be used for comparing groups or units differing in full-time equivalent, funding or the number of researchers,for comparing countries by population, gross domestic product, etc. It is shown that for the calculation of the reduced Hirsch index, the upper part of the original citation distribution is sufficient. The method is illustrated through several case comparisons.
COBISS.SI-ID: 30069465
This study examines the effect of international collaboration of Slovenian authors and the status of journals where papers are published (as determined by their impact factors) on the impact of papers as measured by the number of citations papers receive. Research programme groups working in Slovenia in the2004-2008 period in the fields of physics, chemistry, biology, biotechnology, and medical science were used for analyses. The results of the analyses show that the effects of the two factors differ among the fields. We discuss possible reasons for this, including the possibility that differences are the result of Sloveniaćs science policy.
COBISS.SI-ID: 30085593
Healthcare quality monitoring by the Ministry of Health in Slovenia includes over 100 business indicators of economy, efficiency and funding allocation, which are analysed annually for over 20 hospitals. Most of these indicators are random-denominator same-quantity ratios with a strongly correlated numerator and denominator, and the goal is the identification of outliers. A large simulation study was performed to study the performance of three types of methods: common outlier detection tests for small samples-Grubbs, Dean and Dixon, and Nalimov tests-applied unconditionally and conditionally upon results of Shapiro-Wilk normality test; the boxplot rule; and the double-square-root control chart, for which we introduced regression-through-originbased control limits. Pert, Burr and three-parameter loglogistic distributions, which fitted the real data best, were used with no,one or two outliers in the simulated samples of sizes 5 to 30. Small (below0.2, right skewed) and large (above 0.5, more symmetrical) ratios were simulated. Performance of the methods varied greatly across the conditions. Formal small-sample tests proved virtually useless if applied conditionally upon passed normality pre-test in the presence of outliers. Boxplot rule performed most variedly but was the only useful one for tiny samples. Our variant of the double-square-root control chart proved too conservative in tiny samples and too liberal for samples of size 20 or more without outliers but appeared the most useful to detect actual outliers in samples of the latter size. As a possibility for future improvement and research, we propose pre-testing of normality by using a class of robustified Jarque-Bera tests.
COBISS.SI-ID: 29598681
STUDY OBJECTIVES: Sleep quality commonly diminishes with age, and, further, aging men often exhibit a wider range of sleep pathologies than women. We useda freely available, web-based discovery technique (Semantic MEDLINE) supported by semantic relationships to automatically extract information from MEDLINE titles and abstracts. DESIGN: We assumed that testosterone is associated with sleep (the A-C relationship in the paradigm) and looked for a mechanism to explain this association (B explanatory link) as a potential or partial mechanism underpinning the etiology of eroded sleep quality in aging men. MEASUREMENTS AND RESULTS: Review of full-text papers in critical nodes discovered in this manner resulted in the proposal that testosterone enhances sleep by inhibiting cortisol. Using this discovery method, we posit, and couldconfirm as a novel hypothesis, cortisol as part of a mechanistic link elucidating the observed correlation between decreased testosterone in aging men and diminished sleep quality. CONCLUSIONS: This approach is publically available and useful not only in this manner but also to generate from the literature alternative explanatory models for observed experimental results.
COBISS.SI-ID: 29619673