Coefficient of variance

Reproducibility testing demonstrated that protein abundance measured using the spectral counting method exhibited a Pearson correlation R2 value >0.99 and a coefficient of variance of 14% (Fig. 20.6). 

Analytical variance is defined as the coefficient of variance or relative standard deviation that is directly related to the experimental approach. This variance does differ in accordance with the technology platform being used and is... 

A recovery of 97% was obtained in this method using lOg of clean sediment samples spiked with 777pg oil. The standard deviation was 0.014, and the coefficient of variance=3.47% with n=10. 

Whereas precision (Section 6.5) measures the reproducibility of data from replicate analyses, the accuracy (Section 6.4) of a test estimates how accurate the data are, that is, how close the data would represent probable true values or how accurate the analytical procedure is to giving results that may be close to true values. Precision and accuracy are both measured on one or more samples selected at random for analysis from a given batch of samples. The precision of analysis is usually determined by running duplicate or replicate tests on one of the samples in a given batch of samples. It is expressed statistically as standard deviation, relative standard deviation (RSD), coefficient of variance (CV), standard error of the mean (M), and relative percent difference (RPD). 

The results correspond well with observations of other groups who showed a residual coefficient of variance in IMCL content of about 6% in TA and SOL. Altogether, reproducibility of IMCL is comparable to that achievable for other MR visible metabolites (e.g., in brain) and sufficient for determination of metabolic correlations. It should be mentioned that in contrast to many other metabolites detectable by NMR in vivo inter-individual variations of the IMCL content is markedly higher (up to 20-fold). 

During the period of immersion of the samples in sodium chloride electrolyte, electrochemical noise measurements were made using the electronic apparatus previously described. The time records obtained were analysed using statistical techniques to derive mean, standard deviation and coefficient of variance. 

The Wodicka efal. (1997) paper also defined the performance of fhe Affymetrix chip. Semiquantitative measurement of the absolute abundance of mRNA species was possible. Flybridization of total yeast-genomic DNA to the chips revealed the mean hybridization signal across 6049 probe sets to vary by 25% coefficient of variance (CV). The use of gDNA serves to normalize because most genes are represented only once in the population. In fact, the majority (98%) of the intensities were found to cluster well within two standard deviations. Thus, the concentration of a given mRNA could be estimated af >95% probability to reside within twofold of its actual concentration. Measurement at widely different total gDNA concentrations did not appreciably affect this outcome. 

The coefficient of variance (CV) is 100 times the ratio of the standard deviation divided to the arithmetic mean. 

CV is the coefficient of variance, also known as relative standard deviation ... 

During a screening campaign some plates and even entire batches can fail due to various reasons. To control the quality of plates, during a screen, we use the Z-primes and the Multivariate Z-primes nodes we have developed. Plates failing to fulfill a minimal criterion such as a Z-prime factor above 0.3 are eliminated from further analysis and scheduled for rescreening. A further useful node to verify the quality of plates is the CV node that calculates coefficients of variance for selected parameters. 

The relative % standard deviation (Equation 4.5) is also called the coefficient of variance, c.v. Relative standard deviation relates the standard deviation to the value of the mean and represents a practical and popular expression of data quality. Again, for an entire population of samples, s is replaced by c. 

Equations (8) and (9) show, that separation efficiency is determined by the peak width, in these equations expressed as the coefficient of variance cr2. The smaller is cr2, the narrower is the peak, and hence the greater is the efficiency to separate two neighboring peaks. 

The width of a peak, or, in other words, the length of a solute zone, is affected primarily by diffusion phenomena leading to a broadening of the solute zone. In addition, in capillary zone electrophoresis, zone broadening can be caused by thermal effects, electrodispersion, or adsorptive effects. All these effects can be expressed as coefficients of variance cr2, adding to a total coefficient of variance of the system ofotal ... 

Relative standard deviations (coefficient of variance (CV)) of the position and the intensity are calculated to demonstrate reproducibility. 

Number Protein spots selected spots are indicated in Fig. 3 condition. Protein sample mouse liver lysate 2.3 pg, Number of tested times 5, The values shown in the table are coefficient of variance (CV) (%). The data are summarized in pJand molecular weight (M. W.) directions... 

Species Digestion Procedure % Recovery % Coefficient of Variance... 

This definition is connected with the definition of sensitivity of the method as the concentration of the lowest standard with a coefficient of variance (CV) <20%. 

For internal quality control, urine from a known MPS patient and a solution containing chondroitin sulfate (50 pg/ml) are used. Results for urine and the artificial control should not exceed 3 standard deviations when plotted over time if it does, the test has to be repeated. In addition, absolute absorption values, the slope of the calibration curve, and the coefficient of variance (CV) of duplicates have to be within certain limits defined by the laboratory. 

While thousands of analyses of archaeological bronzes have been reported in the literature, the basis for comparing them, especially those from different laboratories, is shaky. A round-robin project of chemical analyses was attempted to improve the situation. Two ancient bronze objects were milled to a fine powder, sieved, and mixed to a homogeneous mass. Samples of 500 mg each drawn randomly from this mass were circulated, and results were returned from 21 laboratories. Forty-eight elements were analyzed some laboratories did only one element, some did as many as 42. The coefficient of variance (or relative standard deviation) ranges from 4% for Cu up to over 200% for some trace elements. The results are tabulated, and methods are suggested to narrow the spread of results in the next run of this program. 

Standard deviation Coefficient of variance (relative standard deviation), %... 

The type of factors one needs to consider include the sensitivity, specificity, reproducibility, robustness and reliability of the IA. IA, because of their selectivity and sensitivity, lend themselves to a wide range of applications in the food area. They can detect antigens from pg/ml to pg/ml and this can be increased by 2-3 orders of magnitude by use of amplification systems. The coefficient of variance can be from 10-15%. The antigen of interest may be present in a number of different types of food systems and the IA needs to be robust. The reliability of IA has to be monitored carefully there can be... 

In other words, precision of analysis will always be very low for ary influent sample relative to the corresponding effluent sample. This may cause some confusion which would not arise if precision is expressed in other scales for which analyte size need not be stated. One such scale is relative standard deviation (RSD) or the coefficient of variance (CV) which is a ratio of standard deviation to the arithmetic mean of the replicate analyses and expressed as a percent. 

For proteomic technologies to be of widespread use, the reproducibility of each method must be determined. Several studies have been conducted to investigate the coefficient of variance associated with different technologies. One group examined a fully automated HPLC 9.4-tesla Fourier transform ion cyclotron resonance MS designed for unattended proteomics research 24 hours per day to investigate the instruments overall performance. 

Calibration Samples. Monodisperse polystyrene latices are available with known, narrow particle size distributions. Coefficients of variance about the mean diameter are typically less than 6% of diameter measured using electron microscopy (25). HDC typically cannot resolve differences in diameter of only 6%. Therefore, these polystyrenes are sufficiently narrow to be used as HDC calibration reference samples. However, doing so may result in incorporation of a systematic error in the particle size versus elution volume calibration, arising from known electron microscopy errors of as much as 5% for particles below 1 um (26). Therefore, accuracy can only be stated as relative to electron microscopy results for the calibration samples. FlowSizer performance specifications have been reported elsewhere (27) with diameter and mass percent results within 5% of those determined by electron microscopy for a series of these monodisperse polystyrene latices. 

Particle Retention in Column. The results listed in Table II indicate that a significant proportion of the latices with diameters above 200 nm is retained within the HDC column. However, the percent recovered for each sample is very reproducible once the column is conditioned. The last column of Table II lists the coefficient of variance (CV) of the measured areas for the last three injections of each sample. Such low CV values are possible only if the same amount of sample is reaching the detector for each injection. Percent retention of latex within the column must be repeatable, and therefore, predictable. Any predictable (systematic) error which may affect calculated results can be eliminated. The effects of sample retention can be overcome by multiplying K (extinction coefficient) by percent recovery for each sample and using... 

Instrument precision is a measure of reproducibility, i.e., how consistent an instrument is in delivering volume. This is generally measured as a coefficient of variance (CV). Reproducibility for multichannel (96- or 384-tip) pipetting instruments has two aspects. Within-plate variability measures the consistency from one channel to another in the same transfer cross-plate variation measures the consistency of the same channel through multiple transfers. A good liquid handler should be consistent in both functions. 

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