Individual variability

One significant feature of the Parametric Method is that it indicates, through the (1 + K 2) value, the relative contribution of each variable to the uncertainty in the result. Subscript i refers to any individual variable. (1 + K ) will be greater than 1.0 the higher the value, the more the variable contributes to the uncertainty in the result. In the following example, we can rank the variables in terms of their impact on the uncertainty in UR. We could also calculate the relative contribution to uncertainty. 

Many distributions occurring in business situations are not symmetric but skewed, and the normal distribution cui ve is not a good fit. However, when data are based on estimates of future trends, the accuracy of the normal approximation is usually acceptable. This is particularly the case as the number of component variables Xi, Xo, etc., in Eq. (9-74) increases. Although distributions of the individual variables (xi, Xo, etc.) may be skewed, the distribution of the property or variable c tends to approach the normal distribution. 

In practice, a normal distribution is assumed for the individual variable. If other distribution functions are required, the algorithm z = /(CP) in Section 5.1.1, respectively the function FNZ() in Table 5.16 has to be appropriately changed. 

PENG Y s, PENG Y M, MCGEE D L and ALBERTS D s (1994) Carotenoids, tocopherols and retinoids in human buccal mucosal cells intra- and inter-individual variability and storage stability. J Clin Nutr 59(3) 636-43. 

NOAEL (no-observed-adverse-effect level) is defined as the highest dose at which no adverse effects are observed in the most susceptible animal species. The NOAEL is used as a basis for setting human safety standards for acceptable daily intakes (ADIs), taking into account uncertainty factors for extrapolation from animals to humans and inter-individual variabilities of humans. The adequacy of any margin of safety or margin of exposure must consider the nature and quality of the available hazard identification and dose-response data and the reliability and relevance of the exposure estimations. In some cases, no adverse endpoint can be identified such as for many naturally occurring compounds that are widespread in foods. In that case, an ADI Not Specified is assigned. ... 

The squared inter-set correlation coefficients vary from 0.21 to 0.38. Thus, only some 20% to 40% of the variance of the individual variables can be explained by one of the variables from the other data set. At a first glance these low inter-set correlations do not indicate a strong relation between the two data tables. In... 

A major limitation to the value of CCA thus already has become apparent in the example shown. There is no guarantee that the most important canonical variable t, (or U ) is highly correlated to any of the individual variables of X (or Y). It is possible then for the first canonical variable tj of X to be strongly correlated with Uj, yet to have very little predictive value for Y. In terms of principal components... 

There are several good reasons to focus on linear models. Theory may indicate that a linear relation is to be expected, e.g. Lambert-Beer s law of the linear relationship between concentration and absorbance. Even when a linear relation does not hold strictly it can be a sufficiently good local approximation. Finally, one may try and find a transformation of the individual variables (e.g. a logarithmic transformation), in order to obtain an acceptable linear model for the transformed variables. Thus, we simplify eq. (36.1) to... 

In each of these studies dozens of transgenic animals were made and characterized. This is necessary because there is considerable individual variability in phenotype, presumably because of different sized transgene concatemers and different chromosomal integration sites. In some foun-... 

In general, it is easier to measure the permeability coefficient than the partition coefficient, diffusion coefficient, and membrane thickness. Once permeability is measured, it is difficult to separate the contributions of the individual variables. We often see permeability coefficients being reported in the literature instead of the more fundamental partition coefficient and diffusion coefficient being reported separately. 

Heusler-Bitschv S, Knutti R, Schiatter C. 1988. Inter-individual variability of the kinetics of lead in man. In Braetter P, Schramel P, eds. Proceedings of the International Workshop Trace element analytical chemistry in medicine and biology. Vol. 5. April 1988, Neuherberg, West Germany, 627-634. 

The method we will use to illustrate the dimensional analysis process is one that involves a minimum of manipulations. It does require an initial knowledge of the variables (and parameters) that are important in the system and the dimensions of these variables. The objective of the process is to determine an appropriate set of dimensionless groups of these variables that can then be used in place of the original individual variables for the purpose of describing the behavior of the system. The process will be... 

Tab. 4.1 Known causes of individual variability in warfarin therapy in thromboembolism...

Lu AY. Drug-metabolism research challenges in the new millennium individual variability in dmg therapy and drug safety. Drug Metab Dispos 1998 26[12] 1217 1222. 

It has now been established that genetic polymorphisms in drug metabolizing enzymes such as the cytochrome P450s (CYP) and the phase II enzyme, thiopu-rine methyltransferase, are responsible for inter-individual variability in response and adverse reactions [12, 13]. However, at the present time, the impact of poly-... 

The G/A promoter polymorphism at the apoAI gene locus predicts individual variability in fasting and postprandial responses to the HMG CoA reductase inhibitor atorvastatin. Circulation 1999 100(Suppl I) I—239. 

Dose- related increases in thiocyanate were observed, indicating that cyanide is liberated with the metabolism of acrylonitrile. In a study with human volunteers under controlled conditions, 2-cyanoethylmercapturic acid (CMA) was monitored in urine as an indication of exposure. On average, 22% of the absorbed acrylonitrile was metabolized to CMA however, considerable individual variability was observed. The CMA excretion ranged from 13% to 39% of the absorbed dose (Jakubowski et al. 1987). 

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