Relative standard deviation coefficient of variation

The random or indeterminate error associated with a measurement or result. Sometimes called the variability, it can be represented statistically by the standard deviation or relative standard deviation (coefficient of variation) (p. 14). 

The ICH recommends that repeatability be assessed using a minimum of nine determinations covering the specified range for the procedure (e.g., three concentrations/three replicates as in the accuracy experiment) or using a minimum of six determinations at 100% of the test concentration. Reporting of the standard deviation, relative standard deviation (coefficient of variation), and confidence interval is required. The assay values are independent analyses of samples that have been carried through the complete analytical procedure from sample preparation to final test result. Table 1 provides an example set of repeatability data. 

Definition The precision of an analytical method is the extent of the agreement between the measured values in a series of analyses of a homogeneous sample. The precision of a method is normally given by the standard deviation (.S ) or relative standard deviation (coefficient of variation or. Srei). The precision is a measure of the variabUity of the analytical method under normal laboratory conditions. 

Precision Absolute standard deviation, relative standard deviation, coefficient of variation, variance... 

They include simple statistics (e.g., sums, means, standard deviations, coefficient of variation), error analysis terms (e.g., average error, relative error, standard error of estimate), linear regression analysis, and correlation coefficients. 

Thus, for glucose measurement excellent parameters such as a coefficient of variation (relative standard deviation, CV) of 0.2-0.6%, have been achieved by using a flow injection analysis (FIA) device combined with a GDH reactor and an electrode modified for NADH indication (Fig. 39) (Appelqvist et al., 1985). 

Another measure of dispersion is the coefficient of variation, which is merely the standard deviation expressed as a fraction of the arithmetic mean, viz., s/x. It is useful mainly to show whether the relative or the absolute spread of values is constant as the values are changed. 

The relative standard deviation RSD (also known as the coefficient of variation, c.o.v., or CV), which is frequently used to compare reproducibilities, is calculated as... 

The relative standard deviation RSD (or c.o.v. = coefficient of variation ) is constant over the whole range, such as in many GC methods, that is, the standard deviation Sy is proportional to y. 

Coefficient of variation The ratio of the standard deviation to the mean often expressed as a percentage (see also Relative standard deviation). 

There are times when it is desired to describe the relative variability of one or more sets of data. The most common way of doing this is to compute the coefficient of variation (CV), which is calculated simply as the ratio of the standard deviation to the mean, or... 

The coefficient of variation or relative standard deviation expresses the standard deviation as a percentage of the mean value and provides a value which gives an easier appreciation of the precision ... 

It is also clearly seen in Fig. 2.34 that the relative frequency distribution of powder particles remains log-normal starting from Mg through any powder regardless of the duration of reactive milling time. This is exactly the same behavior as already described for mechanically milled commercial MgH powders (Fig. 2.20). The experimental coefficient of variation, CV(ECD) = 5D(ECD)/M(ECD) (where SD is the standard deviation... 

The standard deviation of the measurement error is proportional to the weighted amount of the component. Therefore, the relative standard deviation (or coefficient of variation (cv)) is constant. 

Relative standard deviation srei or RSD % coefficient of variation %CV or %... 

FIGURE 9 Hierarchy of, relationship between, and objectives and requirements for prevalidation [106], validation [62,63, 68], and standardization of analytical methods [62, 63, 67, 68,75,84] RSD = relative standard deviation, CV = coefficient of variation, SOP = standard operating procedure. 

Precision is usually expressed as a standard deviation, variance, or percentage relative standard deviation of a series of measurements. The most useful term is the percentage relative standard deviation (RSD%) or coefficient of variation... 

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