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  • 1990-1994  (3)
  • 1950-1954
  • Intraclass correlation  (2)
  • 3-dimensional  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Bias of maximum likelihood estimator of intraclass correlation (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 421-424 
    Details
    ISSN: 1432-2242
    Keywords: Intraclass correlation ; Maximum likelihood estimator ; Bias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A bias correction was derived for the maximum likelihood estimator (MLE) of the intraclass correlation. The bias consisted of two parts: a correction from MLE to the analysis of variance estimator (ANOVA) and the bias of ANOVA. The total possible bias was always negative and depended upon both the degree of correlation and the design size and balance. The first part of the bias was an exact algebraic expression from MLE to ANOVA, and the corrected estimator by this part was ANOVA. It was also shown that the first correction term was equivalent to Fisher's reciprocal bias correction on hisZ scores. The total possible bias of MLE was large for small and moderate samples. Relative biases were larger for small parametric values and vice versa. To ensure a relative bias less than 10% assuming an intraclass correlation of 0.025, which is not unusual in most of the animal genetic studies, the total number of observations (N) should be not less than 500. From a design point of view, minimum bias occurred atn = 2, the minimum family size possible, underN fixed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588594
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  • 2
    Electronic Resource
    Electronic Resource
    The dilemma of negative analysis of variance estimators of intraclass correlation (1992)
    Springer
    Theoretical and applied genetics 85 (1992), S. 79-88 
    Details
    ISSN: 1432-2242
    Keywords: Intraclass correlation ; Negative estimate ; Restricted maximum likelihood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At least two common practices exist when a negative variance component estimate is obtained, either setting it to zero or not reporting the estimate. The consequences of these practices are investigated in the context of the intraclass correlation estimation in terms of bias, variance and mean squared error (MSE). For the one-way analysis of variance random effects model and its extension to the common correlation model, we compare five estimators: analysis of variance (ANOVA), concentrated ANOVA, truncated ANOVA and two maximum likelihood-like (ML) estimators. For the balanced case, the exact bias and MSE are calculated via numerical integration of the exact sample distributions, while a Monte Carlo simulation study is conducted for the unbalanced case. The results indicate that the ANOVA estimator performs well except for designs with family size n = 2. The two ML estimators are generally poor, and the concentrated and truncated ANOVA estimators have some advantages over the ANOVA in terms of MSE. However, the large biases may make the concentrated and truncated ANOVA estimators objectionable when intraclass correlation (ϱ) is small. Bias should be a concern when a pooled estimate is obtained from the literature since ϱ〈0.05 in many genetic studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223848
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and properties of colorless rigid-rod poly(benzobisthiazole) derived from bicyclo[2.2.2]octane (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2953-2960 
    Details
    ISSN: 0887-624X
    Keywords: benzobisthiazole ; bicyclo[2.2.2]octane ; rigid-rod ; colorless ; 3-dimensional ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycondensation in polyphosphoric acid of 2,5-diamino-1,4-benzene dithiol dihydrochloride with bicyclo[2.2.2]octane-1,4-dicarboxylic acid, as well as the corresponding dimethyl ester or diacid chloride, led to rigid-rod benzobisthiazole polymers. Colorless and soluble polymers with intrinsic viscosities as high as 30.6 dL/g (methanesulfonic acid, 30°C) were obtained. The ultraviolet-visible spectrum of a polymer film cast from methanesulfonic acid under reduced pressure displayed no absorptions in the visible range (400-900 °m). The polymer was thermooxidatively stable up to 420°C in air as determined by thermogravimetric analysis. Fibers spun from a lyotropic polyphosphoric acid solution exhibited a tensile strength of 300-450 Ksi, a modulus of 26 Msi, and a compressive strength of 53 Ksi. Wide-angle X-ray scattering patterns of polymer fibers indicated a 3-dimensional crystal structure rather than a nematic liquid crystal structure. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321517
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    Paper (German National Licenses)
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