THE SHEWHART CONTROL CARDS IN THE ASSESSMENT IN STATISTICA

Abstract

Available statistical programs allow statistical analysis of the data, and enables the use of advanced procedures, including the possibility of using Shewhart control charts in the SPC (Statistical Process Control). Control charts are basic and applied since the thirties of the twentieth century statistical process control tools. The article presents the use of Shewhart control chart when evaluating a number. Presents the X-type control card - the average (arithmetic mean) and R (dehiscence). It is a card that allows control of measurable characteristics of the product or article. Are applied to the card mean values of elements of the measurement results of samples taken at regular intervals from undergoing the process control (where possible from a technical and economic point of view). Analysis of control cards comes down to it, on the basis of the results determine whether the process that is monitored is going well, if it is already the correct time. Control cards with the numerical ratings can be used when the measurement data are normally distributed. In most standard approach we have to deal with two cards and two histograms. One of the cards is called a card X - average, and the second is called the card R. In both graphs the horizontal axis (abscissa) represents the next sample. If the card is X-bar, the vertical axis (ordinate) represents the average value of the test variable (test characteristics), while in the case of R on the card is deleted axis of the variable test interval. X card - minicomputers and R is the most common control card with a numerical evaluation. The purpose of statistical process control is to bring it to a stable and acceptable level, maintaining it at that level, and to ensure compliance with specified requirements for products (goods) or services. The main statistical tool used for this purpose is the control card.