Attribute Charts Results - Brushing Tab
Control Charts for Variables vs. Charts for Attributes
Select the Brushing tab of the Results dialog box to access options to highlight specific samples in your data set.
Include/exclude samples.
The options in the Include/exclude samples box are used to toggle between individual samples in the graph.
Selected
To highlight a specific point (sample), select the Selected option button. You can choose the sample to brush using the Sample <<, >> buttons or by clicking on the numbers in the adjacent box. The box shows the sample labels (numbers) and can be sorted by sample labels (numbers), magnitude of X-bar chart values, or magnitude of R/S chart values by selecting the appropriate option in the drop-down list below the box. Whenever you click on a different sample in the list field, the information shown in the Summary box at the top of the dialog will be updated. You can select multiple samples by pressing the CTRL key and selecting the samples from the list.
All out-of-control samples
Select this option button to automatically highlight all out-of-control samples in the chart. When this option is chosen, the types of out-of-control points will be listed below the option (out of limits, runs violations) giving you an idea of what types of violations have occurred in the data set.
Always select last sample
Select this option button to automatically highlight the last sample in the data set. This option is particularly useful in conjunction with the Show Stats check box (see below) when you are continuously updating the chart. If you select the Always select last sample button, then the Show Stats window will always show the statistics for the most recent sample in the chart.
Including/Excluding points from calculations/graphs
Once you have highlighted the samples of interest, you can further analyze them by excluding them from the calculation of the control limits and process parameters (via the Exclude from computations check box) or excluding them from the graph altogether (via the Exclude (drop) from graphs check box). For example, if we find assignable causes for out-of-control points, we could exclude those points from the computation of process parameters. However, we may still want to display the out-of-control samples in the QC charts. Note that whenever individual samples should be excluded/included from the computations of the control limits, an additional variable must be specified in the data set. This variable will contain sample inclusion codes. This variable can be added during the analysis (via the Setup button, see below).
Assigning Causes and Actions to highlighted samples
Once out-of-control points have been identified (highlighted), you can add labels for causes, actions, or comments to those points. These labels can be used to illustrate why certain points have been excluded from computations of the process parameters.
The data set needs to include separate variables for causes, actions, and additional comments (optional). These variables could be set up prior to the analysis, or they can be created by using the Setup button in the results dialog. See the Causes, Actions, Comments and Data Brushing Setup dialog box for more details on how to create these variables.
Cause
Click the Cause button to label the highlighted point with an explanation of what caused the out-of-control point. When you click this button, a variable selection dialog box will be displayed where you can select the variable that contains the predefined causes. Once this variable is chosen, the Assigning a Cause dialog box will be displayed. Here you can either select from predefined causes or create a new cause.
Action
Click the Action button to label the highlighted point with a brief description of the action taken to correct the situation that led to the out-of-control point. When you click this button, a variable selection dialog box will be displayed where you can select the variable that contains the predefined actions. Once this variable is chosen, the Assigning an Action dialog box will be displayed. Here you can either select from predefined actions or create a new action.
Comment
Click the Comment button to label the highlighted point with any additional comments you have about the out-of-control (or highlighted) point. When you click this button, a variable selection dialog box will be displayed where you can select the variable which contains the predefined comments. Once this variable is chosen, the Assigning a Comment dialog box will be displayed. Here you can either select from predefined comments or create a new comment.
Setup
Click the Setup button to display the Causes, Actions, Comments and Data Brushing Setup dialog box, which is used to create the variables and codes/text values for causes, actions and comments.
Show stats
Select the Show stats check box to show various statistics for the highlighted points. The sample stats (which were requested on the Stats tab of the Options dialog box) will be displayed when you click on the respective individual samples in the list box. The Sample Stats box will display all the requested statistics. This box will update as you select different samples from the drop-down list field.
Show or Hide individual observations
In order to further analyze the out-of-control (or highlighted) samples, you can have the individual observations for those samples displayed in the QC graph. To show the observations, select the Show check box. When the chart is updated, the X-bar chart portion of the QC graph will display the individual observations for the highlighted points.
Note that instead of using this tab to examine individual samples, you can examine points graphically (brushing mode) using the Brush button on the lower part of the Results dialog. See Reviewing Variable Control Charts, Moving Average Charts, and X & Moving Range Charts for more details.