Evaluating Data Representativeness

Data used to describe variation are ideally representative of some population of risk assessment interest. Representativeness was a focus of an earlier workshop on selection of distributions (USEPA 1998). The role of problem formulation is emphasized. In case of representativeness issues, some adjustment of the data may be possible, perhaps based on a mechanistic or statistical model. Statistical random-effects models may be useful in situations where the model includes distributions among as well as within populations. However, simple approaches may be adequate, depending on the assessment tier, such as an attempt to characterize quantitatively the consequences of assuming the data to be representative. 

Application of Uncertainty Analysis to Ecological Risk of Pesticides 

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Evaluated data, representing parametric analysis of data sets, including in some cases judgmental interpretation by one or more experts. 

Table 1 Representative data evaluating data obtained from various studies for calculating the LOD and LOQ values for the extraction/analysis procedure using the 3(RMSE)/slope method to estimate the LOD/LOQ and the 799, j,seloq method to calculate the MDL and MQL...

Evidence for Equilibrium. The lines in Figure 1, as well as those from data obtained on the other two elastomers, have a zero slope over three decades of time, an indication that the data represent elastic (time-independent) properties. Furthermore, the moduli of the elastomers at 5°C, evaluated as illustrated by Figures 1 and 2 and based on the dimensions of the specimens at 5°C, are less than those at 30°C. The ratio Ejq/Ej is 1.06 for the LHT-240 and Tri-NCO elastomers and 1.08 for the TIPA elastomer. These values are only slightly less than 303/278 ( = 1.09) which is essentially the theoretical value for the ratio of elastic moduli at 30° and 5°C. Actually, the data at 5°C showed a slight amount of relaxation during three decades of times. But relaxation was complete at 30°C, as indicated by the above remarks. 

Note Data represent the mean S.E. (n = 3). CLapp, apparent membrane permeability clearance ND, not detected. Absorption was evaluated in our laboratory using the closed loop of the rat colon in situ (urethane anesthesia, 1.125 g/4.5 ml/kg, i.p.) in 60 min for riboflavin and 30 min for the others. 

Note Data represent the mean S.E. (n = 3). MW, molecular weight P0/w, octanol-to-water partition coefficient CLapp, apparent membrane permeability clearance SI, midgut area of the small intestine NA, not available or applicable. Absorption was evaluated in our laboratory using the closed loop of the rat intestine in situ (urethane anesthesia, 1.125 g/4.5 ml/kg, i.p.) in 60 min for riboflavin and L-camitine and 30 min for the others. For those that are transported by carriers in part (riboflavin and glycerol in both colon and SI, and L-carnitine, 5-fluorouracil, and cephradine in SI), absorption was evaluated at higher concentrations where the contribution of carrier-mediated transport is negligible. Values of P0/w were obtained from a report by Leo et al. [30] except for that of D-xylose, which was determined in our laboratory. a Data by single-pass perfusion experiments. b Unpublished data from our laboratory. 

Lotka s intrinsic rate of growth of the population. At an initial position and time, a neutral mutation occurs and afterwards no further identical mutations occur (infinite allele model). We are interested in the time and space dependence of the local fractions of the individuals, which are the offspring of the individual that carried the initial mutation. The goal of this analysis is the evaluation of the position and time where the mutation originated from measured data representing the current geographical distribution of the mutation. We limit our analysis to one-dimensional systems, for which a detailed theoretical analysis is possible. Eqs. (39) and (40) turn into a simpler form ... 

In Section 3.3, the background material developed in Section 3.2 is used in a discussion of practical issues involved in the selection of distributions, particularly for models of pesticide ecological risk. The topics discussed include data representativeness, preliminary data exploration, selection of distribution type, estimation of distribution parameters (distribution fitting), and evaluation of distribution fit. 

The exposure of populations served by CWS to atrazine and simazine in each of the 32 states was evaluated using SDWA compliance monitoring data collected between January 1993 and December 2000 (Tables 29.3 and 29.4). These data represented the best available information from state SDWA agencies in the 32 states. Drinking water data entered into the PLEX database provided a direct link between the population and the estimated concentration of atrazine and simazine in the drinking water. 

The work of this CRP has recently concluded and a report summarizing the results of this task has been prepared. New, highly precise decay data on total and/or partial half-lives for 7 nuclides, a-particle emission probabilities (Pa) for 7 nuclides, and y-ray emission probabilities (Py) for 21 nuclides have been produced. The final list of recommended decay data includes these results, as well as those from other recent measurements, together with carefully evaluated information on a number of other nuclides. In all, this list includes half-life values for 125 nuclides and, for the more prominent transitions only, Pa values for 30 nuclides and Py values for 47 nuclides. [Some of these data represent simply the results of previously published evaluations.] These data will be included in the final report of the CRP, to be published as one of the IAEA Technical Reports Series. 

Qualitative and quantitative acceptance criteria for the PARCC parameters are derived in the planning phase. Whether they are specific statistical values or represent accepted standards and practices, they must be always selected based on the project objectives and be appropriate for the intended use of the data. The DQI acceptance criteria are documented in the SAP and serve as standards for evaluating data quality and quantity in the assessment phase of data collection process. The primary DQIs are established through the analysis of field and laboratory QC samples and by adhering to accepted standards for sampling and analysis. 

Results of the field QC samples (trip blanks, field duplicates, equipment blanks, etc.) are part of the data packages and, together with field samples, they are evaluated to establish whether they are valid. But what is the significance of these data Like the field samples, these data were collected for a well-defined need, use, and purpose. They provide part of the answer to the question Are the data representative of the sampled matrix ... 

Collecting information and its processing will convert them in data. So, data represent agglomerated information, which are partially or finally processed. Examples of data can be found as a parameter, which describe evaluated information to be used for the specific purpose. In this respect the average inlet temperature of cooling water in the condenser is data obtained by the averaging procedure adapted for this purpose. Also heat transfer coefficient used in the design of condenser is the data obtained by the experimental procedure for the heat transfer evaluation. 

Try to present the data that will be evaluated and compared as close together as possible rather than scattered around the table. For example, if the tabular data represent both evaluable and nonevaluable patients who have been either previously treated or previously untreated, place the evaluable patients together rather than present them by previous treatment. 

Even before the anthrax attack in 2001, a variety of detection systems had been developed for potential bioterror agents. A systematic review published in January 2004 identified publicly available articles on 55 such systems (Bravata et al., 2004). Various technologies were represented, including biomass indicators and identification systems targeting toxins, metabolic byproducts, antigens or DNA for selected agents. A key point made by the authors was that only eight of the published articles included evaluation data, and they identified system evaluation as an important area for further research. 

We continue to rely extensively on the two-step (initiation - propagation or autocatalytic) model 4) to evaluate data on coking rates. Two rate constants are involved fc for the deposition of coke on a "clean" surface, i.e., with no coke around and k2 when coke is deposited adjacent to another coke deposit. The former rate constant is for an initiation step (or "non-catalytic" coking), while the latter is for the propagation step (or coking catalyzed by the presence of the coke "product") hence, typically, k2 > ki. A third parameter used in the model is M, which represents the maximum amount of coke which can be deposited on the catalyst. In terms of these three parameters, the coke level expected in a pulse reactor after the passage of R amount of reactant is given by ... 

Material properties are assumed to be constant in the CFD simulation. Data representative of the operating conditions frequently described in the literature [9,11] are used the cell is operated under atmospheric pressure conditions with sulphuric acid solutions at 30 wt% in the cathode compartment and 50 wt% in the anode compartment, as recommended by the Westinghouse cycle efficiency evaluations. The desired specific flow-rate is imposed at the fluid inlet, where the temperature is maintained at 323 K. Adiabatic conditions prevail at the domain boundaries. 

With respect to the amount of data and their different characteristics the data were mapped to the target grids by evaluating a representative mean value for each grid cell by the following procedure ... 

The Thermodynamics Research Center at Texas A M University (TRC) has assembled, collected, evaluated and published tables of thermodynamic data for nearly 60 years. These current volumes describing vapor pressures come from those tables and other evaluation projects conducted by TRC and other research groups, and, as of the publication date, represent all known, evaluated data. The volumes contain constants derived from fitting experimental data with the Antoine and extended Antoine vapor pressure equations. The condensed phases can be either liquid or crystal. Thus, these constants provide evaluated vapor pressures which professional thermodynamicists believe represent the data within experimental error. 

Dispersities of various catalysts evaluated from O2 and CO chemisorption data, represented in Figure 2 reveals that adsorption sites are more dispersed in Cu catalysts than in Cu-Cr catalysts and that dispersities vary with... 

The present compilation of kinetic data represents the 12th evaluation prepared by the NASA Panel for Data Evaluation. The Panel was established in 1977 by the NASA Upper Atmosphere Research Program Office for the purpose of providing a critical tabulation of the latest kinetic and photochemical data for use by modelers in computer simulations of stratospheric chemistry. The recommended rate data and cross sections are based on laboratory measurements. The major use of theoretical extrapolation of data is in connection with three-body reactions, in which the required pressure or temperature dependence is sometimes unavailable from laboratory measurements, and can be estimated by use of appropriate theoretical treatment. In the case of important rate constants for which no experimental data are available, the panel may provide estimates of rate constant parameters based on analogy to similar reactions for which data are available. 

Figure 20.13 The carrier dependent transfection efficiencies measured at media pH 6.5. The HEK 293 cells were incubated with carrier/plasmid DNA complexes for 4 h (with and without FBA) and the transfection efficiencies were observed at 72 h after the transfection. (A) The transfection efficiencies were evaluated by the transfected cellcounting (without FBS). (B) The gene transfections in the presence of 10% FBS. The carrier /DNA weight ratio of COS based carriers was 30 +/ ) and PLL/DNA complex was prepared by the ratio of 2. Data represent mean standard deviations (n = 4). Source From Ref. [75].

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