Welcome to the creating control charts with Minitab webcasts. The main purpose of this webcast is to help you learn how to use Minitab to create and update control charts. This worksheet contains delivery data 10 shipments per day were randomly selected, and the corresponding delivery times were entered into Minitab. For example, here we can see the 10 delivery times for March 4. Then in the next 10 rows, we see the delivery times for March 5, followed by March 6, etc. Now that we have the data arranged in chronological order in Minitab, we are ready to create a control chart to determine if the delivery process is stable over time to create a control chart to stat control charts.
As you can see, Minitab offers many different types of control charts. In this case, we will choose variables charts for subgroups. Because our data are continuous. And because the data were collected in subgroups, we will then choose x bar s to create both an x bar chart and an S chart. There are varying rules of thumb for when to use an x bar chart versus an x bar s chart. And here for our larger subgroup size of 10, we will use x bar s. In the dialog we will use the default option for one column because the delivery times are all in a single column in our worksheet.
Here we will enter the days column and then we will enter our subgroup size of 10 on both the x bar chart The s chart, we can see that all points fall within the control limits and that none of the points are flagged in red. Therefore, we can conclude that this process is stable. Let's now look at some of the editing capabilities. You will notice that the x axis uses a generic sample scale. However, we can replace this generic scale with the dates. To do so just double click on the X axis and under the time tab, select stamp and then enter the date column.
Now let's suppose we get additional data that we need to add to the control chart. Let's go back to the worksheet and enter the new data. To get to the end of the days column. We can click in that column and then use the end key on our keyboard In addition to entering the new data, we will also need to enter the corresponding date to indicate that these deliveries occurred on March 24 2013. To repeat the date, we can hold down the Ctrl key and click and drag with the mouse. Let's now go back to the control chart to update it with the new data.
If we look at the top left corner of the control chart, we will see a yellow symbol. This yellow symbol is warning us that the data in the worksheet have changed since the graph was created. If we right click on it, we will see two update options if we choose automatic updates that chart will always automatically update when the data in the worksheet change. If we choose Update graph Minitab will perform a one time update. In this case, let's choose Update graph. And we can see that the symbol has changed from yellow to green, indicating that the graph is now up to date.
And we can also see that the data for March 24 is displayed on the chart. In addition to the date and automatic update options, there are many other control chart options available in Minitab. For example, you can fix your control limits, and you can plot different stages of your process on the same chart. To learn more about control charts, including which chart to create when we offer elearning, with quality trainer as well as instructor led training. For more information online Quality trainer or our instructor led training, please visit minitab.com