Hey everyone, welcome to this lecture, what is an x bar chart. When dealing with continuous data, it is usually necessary to monitor both the mean value of the measurement and its variation. control of the mean quality level is usually done with the control chart for means, or the x bar chart. Process variation can be monitored with either a control chart for standard deviation, called as the s chart, or control chart for the range called an R chart. The R chart is more widely used. The x bar chart is used when the measurement has a subgroup size that is greater than one and less than eight and the data is continuous.

Let's look at this example. A high voltage power supply should have a nominal output what Stage of 350 volts, a sample of four units is selected each day and tested for process control purposes. The data shown gives the difference between the observed reading on each unit and the nominal voltage times 10. Check if the process is in statistical control. In this example, you are required to measure voltage it is continuous, there are four units selected each day, this the subgroup sizes for here you will be required to perform an x bar chart. So, how to construct this chart?

You will learn that in the next lecture