Control chart definition

Quantitative methods are assays that result in meaningful numeric measurements for a characteristic of a product. Quantitative methods are used in assessing whether final product meets specifications. They are also used to measure product quality (or quantity) in various stages of manufactuiing and the results are often used in quality control charts. Validation is an objective process used to determine whether a quantitative method is performing as expected and is appropriate for its intended use. This chapter provides the motivation behind validation, some terms and definitions used in validation, a consolidated statistically sound approach to validation, along with appropriate statistical analysis, and reporting of validation results. A hypothetical but realistic example is presented and is used to illustrate the validation process. 

Probably the location of the raw materials of an industry contributes more toward the choice of a plant site than any other factor. This is especially noticeable in those industries in which the raw material is inexpensive and bulky and is made more compact and obtains a high bulk value during the process of manufacture. The supply of the basic raw materials should be controlled directly by the user tonnage items like coal, salt, limestone, etc., should be available on company-owned property on the plant site or reached by not too distant pipeline, rail, or water transportation. Surveys should be made to chart definitely the quantity and quality of the basic raw materials a minimum supply of 30 to 50 years is usually considered mandatory. The steel mills are located near the iron mines or at some intermediate point between the iron and the... 

Control Charts—h picture is worth a thousand words, and this is definitely true of the QC data as well. A chart based on statistical control limits must be plotted and interpreted on time. A control chart by itself can only indicate that there is an upset and not the cause of the upset. Laboratory staff must investigate, identify, and eliminate the cause(s) of the upset and bring the process back to a state of statistical control. If a control chart is merely plotted and filed away without taking action when required it is simply a waste of time and effort. 

Clearly, the term nonrandom trend must be consistently defined for the shop floor operators. Such definitions are made by the consistent adoption of rules for judging the current status of a process. Probably the most common set of rules for examining the state of the process is known as the AT T runs rules (AT T 1985). In AT T (1985), these rules are called Tests for Instability. In applying these tests, each half of the control chart (the area between the CL and UCL and the CL and LCL) is divided into three equally spaced zones, as shown in Figure 7. 

American Society for Quality Control. American National Standard. Definitions, Symbols, Formulas, and Tables for Control Charts, 1987. 

When control charts are developed for abnormal data distributions, as in the studied case, the results are as saw in Figure 3. In this figure, the control graph for the THDV of the LI phase of Sample A shows a very high number of outliers, 37 out of a set of 39 elements, which is totally contrary to the definition of outlier in section 2 of this work. This behavior persists even when submitting the data set to a Box-Cox transformation in an attempt to correct the distribution bias, the differences of the variances on the time axis or the possible nonlinearity of the data. 

The use of Shewhart control charts with multiple decision rules provide a more sensitive and reliable quality control than Shewhart control with simple decision rules. However, it should be noticed that the multiple decision rules are only valid if the conventional true value pt and the standard deviation oy are known. In practice this means that (jl-t is traceable to a certified reference material (CRM) or established using a definitive method by a validated laboratory [5], and 0-7 is established by method evaluation with a sufficiently high number of method evaluation samples. 

The basic condition of the Standard application - the availability of stable coupled probabilistic or the multiple probabilistic relations between then controlled quality indexes and magnetic characteristics of steel. All the probabilistic estimates, used in the Standard, are applied at confidence level not less than 0,95. General requirements to the means of control and procedure of its performance are also stipulated. Engineers of standard development endeavoured take into consideration the existed practice of technical control performance and test at the enterprises that is why the preparation of object control for the performance of nondestructive test can be done during the process of ordinary acceptance test. It is suggested that every enterprise is operated in correspondence with direct and non-destructive tests, obtained exactly at it, for detailed process chart and definite product type, however the tests have long since been performed after development of the Standard displayed that process gives way to unification. 

Because of these considerations, it is best to view the charts as a snapshot of the status of state gun control laws in 2004 rather than as a definitive reference. 

The machine-based PSFs include characteristics of the human-system interface and the responses that the machine is designed to provide. Malfunctioning indicators are not a machine-based PSF, they are a situation-based PSF. However, poorly designed indicators are a machine-based PSF. In this PSF flame-work, HSI includes control panels and other traditional HSI elements, but it also includes the accessibility (as designed) of machine components and plant areas. This expanded definition of HSI covers humans obtaining output fl om displays and charts, and it also covers humans providing input to the machine through software, buttons and dials, mechanical tools, or other contact. 

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