Precision of an analytical method

The precision of an analytical method is a measure of the variability of repetitive measurements. Contributions from numerous sources affect precision, but the major components are within-laboratory (repeatability) and between-laboratory (reproducibility) variations. Precision is expressed as the relative standard deviation (or CV)... 

The precision of a test method is the variability between test results obtained on the same material using a specific test method (ASTM, 2004 Patnaik, 2004). The precision of a test is usually unrelated to its accuracy. The results may be precise, but not necessarily accurate. In fact, the precision of an analytical method is the amount of scatter in the results obtained from multiple analyses of a homogeneous sample. To be meaningful, the precision study must be performed using the exact sample and standard preparation procedures that will be used in the final method. Precision is expressed as repeatability and reproducibility. 

The precision of an analytical method is usually expressed as the standard deviation or relative standard deviation (coefficient of variation) of a series of measurements. Precision represents repeatability or reproducibility of the analytical method under normal operating conditions. Precision determinations permit an estimate of the reliability of single determinations and are commonly in the range of 0.3 to 3% for dosage form assays. 

The precision of an analytical method can be defined as the pattern of variation of single assays on a uniform sample. The precision serves to identify random errors and is described by the repeatability (variability within a laboratory) and reproducibility (variation between different laboratories). 

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. 

We can easily quantify measurement error due to existence of a well-developed approach to analytical methods and laboratory QC protocols. Statistically expressed accuracy and precision of an analytical method are the primary indicators of measurement error. However, no matter how accurate and precise the analysis may be, qualitative factors, such as errors in data interpretation, sample management, and analytical methodology, will increase the overall analytical error or even render results unusable. These qualitative laboratory errors that are usually made due to negligence or lack of information may arise from any of the following actions ... 

The precision of an analytical method is the degree to which individual determinations of a series of standards agree. Since in general only one laboratory is involved in the development of the method the precision, as determined by one laboratory by one operator over a relatively short time, is defined as repeatability r (ISO 1994 compare also Section 10.2.3). 

It is often easier to comprehend the degree of variability in a set of data if we express it in relative terms. A typical example of this is when we want to express the precision of an analytical method. 

Determination Determine the precision of an analytical method by assaying a sufficient number of aliquots of a homogeneous sample to be able to calculate statistically valid estimates of standard deviation or relative standard deviation (coefficient of variation). Assays in this context are independent analyses of samples that have... 

Precision is defined as the closeness of agreement between independent test results obtained under stipulated conditions . The precision of an analytical method is evaluated by making repeat independent measurements on identical samples to determine the spread of results. 

The precision of an analytical method is the closeness of a series of individual measurements of an analyte when the analytical procedure is applied repeatedly to multiple aliquots of a single homogeneous volume of biological matrix [16], The precision is calculated as coefficient of variation (C.V.), i.e., relative standard deviation (RSD). The measured RSD can be subdivided into three categories repeatability (intra-day precision), intermediate precision (inter-day precision) and reproducibility (between laboratories precision) [16, 78, 79, 81],... 

The dynamic range of a mass spectrometer is defined as the range over which a linear response is observed for an analyte as a function of analyte concentration. It is a critical instrument performance parameter, particularly for quantitative applications, because it defines the concentration range over which analytes can be determined without sample dilution or preconcentration, which effects the accuracy and precision of an analytical method. Dynamic range is limited by physiochemical processes, such as sample preparation and ionization, and instrumental design, such as the type of mass analyzer used and the ion detection scheme. 

For the precision of an analytical method not only the repeatability of single measurements but also the errors in the calibration procedure should be included. This is a complex problem, because according to the nature of the signal noise, the precision obtainable may vary considerably with the concentration level. In the case of a calibration the scattering of the measured Y, values around the calibration curve is given by the standard deviation of the regression ... 

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. 

Repeatability The precision of an analytical method, usually expressed as the standard deviation of independent determinations performed by a single analyst on the same day using the same apparatus and method. (Section 2.7)... 

The precision of an analytical method is obtained from multiple analyses of a homogeneous sample. You can determine overall precision of the method, including sample preparation. Such precision data are obtained by one laboratory on one day, using aliquots of the homogeneous sample that have been independently prepared. Such interlaboratory precision is called repeatability. Interlaboratory precision, if appropriate, is also determined as part of a measurement of reproducibility or robustness of the method (see below). 

PrecUion describes the reproducibility of results, that is, the agreement between numerical values for two or more replicate measurements, or measurements that have been made in exactly the same way. Generally, the precision of an analytical method is readily obtained by simply repealing the measurement. 

As we have seen, proficiency testing schemes allow the competence of laboratories to be monitored, compared and perhaps improved. By contrast a collaborative trial (CT) aims to evaluate the precision of an analytical method, and sometimes its ability to provide results free from bias. It is normally a one-off experiment involving expert or competent laboratories, all of which by definition use the... 

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