Sökning: "unbiased"

Visar resultat 6 - 10 av 223 avhandlingar innehållade ordet unbiased.

  1. 6. Some advances in Respondent-driven sampling on directed social networks

    Författare :Jens Malmros; Tom Britton; Fredrik Liljeros; Simon Frost; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematical Statistics; matematisk statistik;

    Sammanfattning : Respondent-driven sampling (RDS) is one of the most commonly used methods when sampling from hidden or hard-to-reach populations. The RDS methodology combines an improved snowball sampling scheme with a mathematical model that is able to produce unbiased population estimates given that some assumptions about the actual recruitment process are fulfilled. LÄS MER

  3. 7. Methodology for Handling Missing Data in Nonlinear Mixed Effects Modelling

    Författare :Åsa M. Johansson; Mats O. Karlsson; Andrew C. Hooker; Leon Aarons; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Pharmacometrics; population models; censored observations; missing covariates; missing dependent variable; missing data mechanism; missing completely at random MCAR ; missing at random MAR ; missing not at random MNAR ; estimation algorithms; Pharmaceutical Science; Farmaceutisk vetenskap;

    Sammanfattning : To obtain a better understanding of the pharmacokinetic and/or pharmacodynamic characteristics of an investigated treatment, clinical data is often analysed with nonlinear mixed effects modelling. The developed models can be used to design future clinical trials or to guide individualised drug treatment. LÄS MER

  4. 8. Varince component estimation in geodetic networks

    Författare :Tomas Egeltoft; Lars Sjöberg; []
    Nyckelord :;

    Sammanfattning : A summary of some of the existing variance component estimators are given, namely the MINQE, the IMINQ, the general case of BQUNE (best Quardratic Unbiased Non negative Estimator), the Helmert estimators, the Förstner estimator and the Kubik estimator. A derivation of a special case of the BQUNE is made. LÄS MER

  5. 9. Survey estimation for highly skewed data

    Författare :Forough Karlberg; Chris Skinner; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Extreme values; skewed populations; model-based inference; superpopulation; lognormal distribution; statistik; Statistics;

    Sammanfattning : Estimation of the population total of a highly skewed survey variable from a small sample is problematic if straightforward methods are used since (i) when there are no extreme values in the sample, too small estimates will be obtained (ii) if extreme values are sampled, the estimates will become grotesquely large. Traditional methods for outlier treatment will usually compensate for outliers in the sample, thereby avoiding (ii), whereas the small negative bias of (i) will persist. LÄS MER

  7. 10. Infections in skin cancer

    Författare :Laila Sara Arroyo Mühr; Karolinska Institutet; Karolinska Institutet; []
    Nyckelord :;

    Sammanfattning : The increasing prevalence of skin cancer results in that it will soon equal that of all other cancers combined. Sun exposure is a well-known risk factor for its development, but despite the growing public awareness of the harmful consequences of ultraviolet radiation, the cancer incidence continues to increase, implying that other factors might also have a role in promoting this disease. LÄS MER