Shewhart Control Charts |
Control charts are constructed to decide whether a process is under statistical control and to monitor any departures from this state. This means that stability of some process properties over time is tested using certain statistical assumptions about the process (data it produces). Commonly considered properties are mean, variance (standard deviation), distribution shape or proportion of faulty items. The Shewhart control charts were invented in 1932. They are based on monitoring events, which are very unlikely when the controlled process is stable. Any incidence of such an event is taken as an alarm signal suggesting that stability of the process was broken and the process changed. Upon receiving such signal, possible causes of the change should be investigated and some correcting steps taken. One example of such an unlikely event is the situation when the control limits (UCL or LCL) are exceeded.
Special features:
X-Bar Charts for data with missing cells
Charts for asymetric data X-Bar and S / R X-Individual and R NP, P, C, U - Charts Shewhart Control Charts - Pdf manual
Examples
X-Bar Chart Output Protocol:
Different types of control chart constructed by QC-Expert
Regular Control Chart X-bar / X-Individual and R: X-Bar and S Chart for unequal group size Chart X-individual and R for asymetrically distributed data using Transformation NP Chart for attributes P Chart for attributes C Chart for attributes U Chart for attributes |