Charts Control charts, also known as Shareware charts are tools used to determine if a manufacturing or business process is in a state of statistical control. The control chart was invented by Walter A. Shareware, (also known as the father Of statistical quality control) while working for Bell Labs in the asses. The company’s engineers were seeking to improve the reliability Of their telephony transmission systems. The engineers had realized the importance of reducing variation in a manufacturing process.
Shareware framed the problem in terms Of Common and facial causes variation and in 1324 introduced the control chart as a tool for distinguishing between the two. Dry. Shareware created the basis for the control chart and the concept of a state of statistical control by carefully designed experiments. Control charts in simpler terms are graphs used to study how a process changes over time. Data are plotted in time order. A control chart consists of a central line for the average, an upper line for the upper control limit and a lower line for the lower control limit.
These lines are determined from satirical data. It includes points representing a statistic of measurements including things like mean, range or proportion of a quality characteristic in samples taken from the process at different times the data. By comparing current data to these historical lines, one can draw conclusions about whether the process variation is consistent (in control) or is unpredictable (out of control). The standard or standard deviation of the statistic is also calculated using all the samples.
The chart may have other optional features, including labels such as peer and lower warning limits, drawn as separate lines, typically two standard errors above and below the centre line. When interpreting control charts, we must understand that it represents a picture off process overtime. To effectively use control charts, one must be able to interpret the picture. The chart above is an example Off stable or in control process. The characteristics that make this chart appear stable are the fact that most points are near the average and some points are near the control limits.
NO points are shown to beyond the control limits. The chart above represents an out of control process as one point is displayed above the upper control limit and one is displayed below the lower control limit. Points that fall outside the control limits are an indication of special causes of variance. This source is usually easy to determine and eliminate, In the business world as well as many other fields, control charts are used to reveal and keep track of pertinent information depending on what aspect is being studied. The above control chart is one used by Walter. We can determine that the chart was out to control.
This particular chart is used in order to estimate the percentage of items that are defective from a supplier, Sample percentages must stay within limits to keep the process going. Once there is a sample percentage outside those limits, the process is stopped. At this point the company would look for an assignable cause. Most frequently this can be cause by a change in material that they use to make an item. This is the most widely used method of quality control among the company’s practices. Another way we use control charts in our daily life if When measuring weight joss over a period of time.
Here it is clear to see that the person to whom the data pertain has experienced a steady rate Of weight loss over a three week period. Using a control chart for this type of scenarios helps one to see the trend Of weight either lost or gained over a specific period of time. The purpose Off control chart is to detect any unwanted changes in your process. For example if you notice Saturday and Sundays your weight is stagnant, you can look back and pay closure attention to activities done on those day such as eating out with friends on the week.
Of all the tools for analyzing data, the control chart is the most useful, It is used in everything from healthcare, to business to simple personal use of documenting things like weight loss, Consistent high quality has become a requirement in today’s competitive market when it comes to business and retail. These charts help to simplify understandings of a process studied and determine what may be the cause. The control chart can be seen as part of an objective and disciplined approach that enables correct decisions regarding control of the process, including whether or not to change process control parameters.
