Basic tools of quality control control chart histogram Pareto chart check sheet cause-and-effect diagram flowchart scatter diagram
control chart / Shewhart chart / process-behaviour chart used to determine whether a manufacturing or business process is in a state of statistical control or not: if the chart indicates that the process is currently under control then it can be used with confidence to predict the future performance of the process; if the chart indicates that the process being monitored is not in control, the pattern it reveals can help determine the source of variation to be eliminated to bring the process back into control;
A control chart consists of the following points representing measurements of a quality characteristic in samples taken from the process at different times; a centre line, drawn at the process characteristic mean which is calculated from the data; upper and lower control limits that indicate the threshold at which the process output is considered statistically 'unlikely'
The chart may contain other optional features upper and lower warning limits, drawn as separate lines, typically two standard deviations above and below the centre line; division into zones, with the addition of rules governing frequencies of observations in each zone; annotation with events of interest, as determined by the Quality Engineer in charge of the process's quality;
Ishikawa diagram / fishbone diagram / cause-and-effect diagram brainchild of Kaoru Ishikawa, who pioneered quality management processes in the Kawasaki; diagram that shows the causes of a certain event; first used in the 1960s; known as a fishbone diagram because of its shape, similar to the side view of a fish skeleton; can reveal key relationships among various variables, and the possible causes provide additional insight into process behaviour ;