Relative percentage deviation

Goodness-of-fit of the proposed model with experimental data is represented by the mean relative percentage deviation modulus a (%) which is defined as ... 

The relative standard deviation is also known as the coefficient of variation (CV). The RSD is often expressed as a percentage ... 

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

Figure 6.18 presents example chromatograms obtained during the evaluation of retention time and peak area reproducibility across the 24 columns (within a single composite run). Table 6.1 lists the average retention time reproducibility and peak area reproducibility values obtained across 24 columns for a total of 24 composite runs (column to column within run). Reproducibility values are expressed as percentage relative standard deviation (%RSD). 

Calculate the percentage of Na2C03 in the sample, and record at least a sample calculation in your notebook, along with all results and the average. Calculate the ppt relative standard deviation. If your three results do not agree to within 10.0 ppt relative standard deviation, repeat until you have three that do or until you have a precision satisfactory to you instructor. 

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 ... 

Fig. 3. Relation between the minimum number of units in a sample require for sampling errore (relative standard deviations in percentage) of 0.1 and 1 % (y-axis) and the overall composition of a sample (x-axis), for mixtures having two types of particles with a relative difference in composition ranging from 100 to 10% Reprinted wiA permission from W. E. Harris, B. Kratochvil, Analytical Chemistry, 46 (1974), p. 314. Copyright 1974 American Chemical Society...

Note This function if given as an empirical relationship between the precision of an analytical method and the concentration of the analyte regardless of the nature of the analyte, matrix, and method used. Acceptable RSDr and RSDr values according to [75] and to AOAC International [56, 62] % RSD = percentage relative standard deviation, PVM = peer-verified methods program. 

In analytical chemistry, the ratio of the standard deviation to the mean, or RSD is often quoted. This quantity is also known as the coefficient of variation (CV), but the term is no longer favored and RSD should be used. Remember both the mean and the standard deviation have the units of the measurand. The relative standard deviation has unit one and is usually expressed as a percentage. 

S. D. , standard deviation of procedure, Vxo relative standard deviation of procedure confidence intervall, 95% data in parenthesis give size as percentage of base peak. 

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... 

The quantity n — 1 in Equation 4-2 is called the degrees of freedom. The square of the standard deviation is called the variance. The standard deviation expressed as a percentage of the mean value (= 100 X s/x) is called the relative standard deviation or the coefficient of variation. 

Radiochemical yields are within 46-74%. The average relative standard deviation of the method is 8%. The accuracy of the method was checked by analysis of a U. S. Geological Survey rock standard. Gallium concentrations in 101 coals, calculated from the concentration in the coal ash and the percentage of low-temperature ash in the coal, range from 1.1 to 7.5 ppm, the median value being between 2.9 and 3.0 ppm (16). 

Relative standard deviation (R.S.D.) and percentage deviation less than 8% (AT and HAT)... 

As the number of data points becomes larger, the value of 5 approaches that of a. When n becomes as large as 20, the equation for a may be used. Another term commonly used to measure variability is the coefficient of variation (CV) or relative standard deviation (RSD), which may also be expressed as a percentage ... 

A reported relative standard deviation of 1—2% for small sets of replicate analyses is common in many recent papers employing this technique. Results falling within 0.10% of the theoretical percentage of oxygen in samples containing about 50% oxygen based on 32 replicate determinations have been reported a4>. For the 32 determinations the relative standard deviation for the data was approximately 0.3%. This level of accuracy and precision is certainly adequate for most analytical purposes. 

The limit of quantitation, as opposed to the limit of detection, is the most important attribute of the swab method because it has been previously determined, from a safety and cross-contamination standpoint, that residual material above the cleaning acceptance limit is of serious concern. The LOQ is defined as a percentage relative standard deviation (percent RSD) of 10%, and the LOD is defined as a percentage RSD... 

Note The relative standard deviation of the percentage recovery of the organic residues from the Chromosorb 104-Amberlite XAD-4 SPE column ranged from 3.5% for 1,3-DNB to 5.5% for DPA. 

Panderi and Parissi-Poulou developed a microbore liquid chromatographic method for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical dosage forms [30]. The use of a BDS C-18 microbore analytical column was found to result in substantial reduction in solvent consumption and in increased sensitivity. The mobile phase consisted of a mixture of 25 mM sodium dihydrogen phosphate buffer (pH 4.8) and acetonitrile (11 9 v/v), pumped at a flow rate of 0.4 mL/min. Detection was effected at 250 nm using an ultraviolet absorbance detector. The intra- and inter-day relative standard deviation values were less than 1.25% (n = 5), while the relative percentage error was less than 0.9% (n = 5). The detection limits obtained according to the IUPAC definition were 0.88 and 0.58 pg/mL for benazepril hydrochloride and hydrochlorothiazide, respectively. The method was applied to the quality control of commercial tablets and content uniformity test, and proved to be suitable for rapid and reliable analysis. 

Analytical data obtained for the said CRMs were acceptable, with recovery percentages varying between 80 and 120 percent depending on the element. Only for elements for which the measured concentrations were very close to the LoDs, namely V in the NIST 1547, Sb in the NIST 1567, and B in the NIST 1547 and 1573, did the recovery worsen to 140, 170 and 70 percent, respectively. Precision was also found to be satisfactory, with relative standard deviations (RSDs) always lower than 20 percent, with the only exception being Sr in the NIST 1567 (28 percent). Higher RSD values were found for elements present at concentrations lower than 0.1 ig g-1 as reported for the Wheat Flour, NIST 1567. 

The precision of an analysis is most conveniently defined in terms of percent relative standard deviation. The standard deviation is relatively easily calculated following a series of discrete measurements either of absorbance or of concentration. The relative standard deviation is then defined as the standard deviation expressed as a percentage of the mean of the data used to calculate the standard deviation. 

EXAMPLE 27-3 A sample is composed of uniform particles of a mineral of density di — 5.2 and a gangue of density d2 = 2.7. The percentage Pi of metal in the mineral is 75, and the percentage Pj in the gangue is 5. If the sample contains P = 60% metal, how many particles must be taken to ensure a relative standard deviation of less than 1 ppt (0.1%) in P, due to sampling error ... 

Precision. The precision of a method is the degree of scatter of the results and is usually reported as a percentage relative standard deviation. It is often subdivided into repeatability (precision on replicate measurements of the same solution) and reproducibility (precision of the results from measurements of different solutions, i.e. of the complete method). 

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