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Träfflista för sökning "WFRF:(Petzold Max 1973) ;srt2:(2000-2004);hsvcat:1"

Sökning: WFRF:(Petzold Max 1973) > (2000-2004) > Naturvetenskap

  • Resultat 1-7 av 7
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1.
  • Petzold, Max, 1973 (författare)
  • A comprative study of some approaches for constructing tolerance limits
  • 2000
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In a dose finding study the aim is to come up with a safe and efficient drug administration. By comparing the obtained tolerance limits with predetermined desired concentration limits, i.e. the therapeutic window, one may be able to adjust the drug dosage. For drugs with a therapeutic window situated at high concentrations close to toxic levels, one has to balance between attaining a high proportion of the population at efficient high levels on one hand and the risks of an overdose on the other hand. In such cases it is important to use the proper estimation approach for the upper tolerance limit. Here a conservative estimation approach intended for a drug with potentially adverse side effects with minor overdoses is compared with an approach intended for a drug with harmless side effects. It is shown that the conservative approach can be considerably less efficient when used in the latter case, a disadvantage that is rarely discussed when proposing conservative estimators. The properties of the two approaches are evaluated using well-known parametric and non-parametric estimators in a simulation study for small and moderate sample sizes.
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  • Petzold, Max, 1973, et al. (författare)
  • Maximum Likelihood Ratio based small- sample tests for random coefficients in linear regression
  • 2003
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Two small-sample tests for random coefficients in linear regression are derived from the Maximum Likelihood Ratio. The first test has previously been proposed for testing equality of fixed effects, but is here shown to be suitable also for random coefficients. The second test is based on the multiple coefficient of determination from regressing the observed subject means on the estimated slopes. The properties and relations of the tests are examined in detail, followed by a simulation study of the power functions. The two tests are found to complement each other depending on the study design: The first test is preferred for a large number of observations from a small number of subjects, and the second test is preferred for the opposite situation. Finally, the robustness of the tests to violations of the distributional assumptions is examined.
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7.
  • Petzold, Max, 1973, et al. (författare)
  • Surveillance in Longitudinal Models: Detection of Intrauterine Growth Restriction
  • 2004
  • Ingår i: Biometrics. - 0006-341X. ; 60:4, s. 1025-1033:60, s. 1025-1033
  • Tidskriftsartikel (refereegranskat)abstract
    • Summary. A new methodology for online detection of intrauterine growth restriction (IUGR) is proposed where traditional methods for statistical surveillance are applied. Here, deficient growth rate is used to detect IUGR instead of the common surrogate measure "small for gestational age" (SGA). Fetal growth is estimated by repeated measurements of symphysis-fundus (SF) height. At each time point the new method, based on the Shiryaev-Roberts method, is used to evaluate the growth in SF height. We use Swedish data to model a normal growth pattern, which is used to evaluate the capability of the new method to detect IUGR in comparison with a method used in practice today. Results from simulations indicate that the new method performs considerably better than the method used today. We also illustrate the effect of some important factors which influence the detection ability and illuminate the tendency of the method used today to misclassify SGA cases as IUGR.
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  • Resultat 1-7 av 7

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