Data monitoring started with Walter A. Shewhart, the “ father of quality ” who developed control charts and demonstrated that common cause and special cause variation exists in every system.

His use of control charts illustrated how stable or unstable a system was with simple charts and graphs. Many managers today, if asked whether their company ’ s system is stable, will not have a clue what you are talking about. In fact, most would not have an idea how to use data to demonstrate that stability.

At this time, only the methods used to provide process control data are involved in our analysis, the specifi c type of chart comes later after determining what is to be monitored and by what means. Which reviews the different types of quality control charts and quality methods.

Personnel who use and understand control charts often use a sample size of fi ve for data analysis on typical X – bar and R charts. The reason for this is that during the Second World War, the U.S. Department of Defense had to teach untrained personnel to measure the quality of the products they made.

The sample size answer was five, because if you take any group of five numbers, add them up, double the sum, and then move the decimal point one place to the left, you will have the average. Shewhart preferred a sample size of four.

The same type of reason was used for the time interval for collecting data, every hour, because teaching personnel to calculate a true sampling plan would have distracted them from their output, which was more important.

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