Right-click the control chart and select View SVG The control chart appears in a new browser window.

2. Use the web browser print function to choose the "Landscape" orientation and print.

Process Analysis control chart troubleshooting

This section explains troubleshooting methods for some Process Analysis control chart problems that can occur.

The bottom graph of my control chart is a zero flat line

Your X-bar & range or X-bar & standard deviation control chart has a range or standard deviation graph with a zero flat line.

Cause: The Process Analysis engine retrieves one row per sample unit from the query. The standard deviation and range statistics are computed based on a single, aggregated figure, and therefore return zero for each sample unit.

Action: Remove the aggregate function from the measure object.

The sampling list in my control chart is empty

The sampling list is empty in the "Data Collection" step of the Process Analysis "New Control Chart" wizard.

Cause: When you create an "Individuals & Moving Range" or "Moving Average & Moving Range" control chart where the sampling list is empty, the appropriate sampling is not available. The "New Control Chart" wizard filters the sampling list to systematic samplings the size of 1.

Action: Create a systematic sampling of size 1.

The limits and center line do not appear on my control chart

Even though you specified the auto-calculation limits, the run line is displayed alone.

Cause: The baseline is wider than the chart history. Action: Do one or more of the following:

• Reduce the baseline limits calculation to match the chart span and refresh the chart.

• Bring in more history.

• Wait the amount of time necessary for the chart span to meet the baseline calculation.

The run line shows the same value continuously in my control chart

The control chart run line shows the same value.

Cause: The Process Analysis engine issues one query for each hourly sample for a control chart that has the time-based hourly setting based on a universe that uses the following date prompts:

• @Prompt('BEGIN_DATE','D',,mono,free)

The time predicate includes the day element but is missing the time. All hourly queries for a given day are the same, and therefore return the same results.

Action: Replace the date prompts with date-time prompts in the fact_ta ble.fact_timestamp:

• @Prompt('BEGIN_DT','D',,mono,free)

• @Prompt('END_DT','D',,mono,free)

The control chart does not show a new member in the existing group

The control chart does not show a new member of a group.

For example, you created a control chart called Cost by Department and a new department has just been added to the source database. However, this new department is not in the control chart, even though you have refreshed the chart.

Create a new control chart for the group.

Process Analysis alerts do not work on my new repository

You have a new repository on which you have defined control charts and alarm rules, but the alert does not work, even though red circles show on the graph.

Create the following alerts in Performance Manager in the "Rules" sub-tab:

• SPCAlert

This rule needs to have a Public scope and have the following rule description:

On this named event: SPCAlert if a condition is met, create the alert: SPC Alert.

• SPCMail

This rule needs to have a Public scope and have the following rule description:

On this named event: SPCMail if a condition is met, send an email.

For more information in creating rules, see the Performance Manager documentation.

Decimals do not show on the control chart

The numbers displayed in the legend of the control chart appear truncated without decimals.

In the source universe of the control chart, assign a number format to the measure with the right-click menu. In Dashboard and Analytics Setup, update the universe and check the properties of the measure object to verify that the number format is updated.

Large numbers overlay the control chart border

The control chart analytic is plotting large numbers that go over the graph border.

Apply a /1000 transform to the SQL of the measure object on which the control chart is based, and assign a custom format using the right-click menu. Make sure you update the universe in Dashboard and Analytics Setup. Click the measure object to see the number format in the universe set up screen. You must purge and refresh the control chart to see the new format in the analytic.

The EWMA run is identical to the Shewhart run in my control chart

You specified a weighting factor of '1'. The EWMA computation assigns a 100% weight to the X-bar current sample, while 0% is assigned to the previous samples.

It is common practice to use a weighting factor between 0.05 and 0.25. Specify a weighting factor of 0.2 to assign a 20% weight to the current sample.

Building a dashboard with too many control charts

If you have created many control charts and you want to include them in a corporate dashboard, you do not have to go through the Dasboard Builder "Create New Analytic" workflow for each control chart.

Use the Control Chart applet as an analytic. In the edit mode of a dashboard, select Toolbox > Analytics Services > Control Charts.

Whenever a control chart is created, it automatically appears in the corporate dashboard. The end user selects a control chart from the list on the left and the control chart appears on the right.

The control chart takes a long time to refresh the first time

Cause: You created a control chart using a time-based sampling (such as Every Hour); the initial refresh of the chart can take a long time.

For example, if the raw source data starts September 1st 2004 and the sampling start date has been specified as 'January 1st 2004', the Rules engine runs one query for each hour starting Jan 1st. Useless queries (24x30x8) are run.

Action: Use a more precise sampling. In the example, you use the start date 'Sept 1st 2004'.

Note:

This issue does not occur with systematic samplings that use one single query for all periods from start date to current date.

Related Topics • What is a sampling?

Displaying time periods on the X axis of the control chart

You created a Process Analysis control chart using a time-based sampling but you cannot display the time on the X axis.

Problem: The control chart shows the sample number on the x-axis with the time period exposed only in the tool-tip.

Resolution: Use a custom Desktop Intelligence report using the 'Control charts' universe (CI_SPC.unv) to display the period on the x-axis.

Specification limits do not show on the control chart

You have defined Specification limits for a control chart but only the control limits appear in the analytic.

The control chart analytic allows you to plot the control limits, not the specification limits. Specification limits apply to individual measurements, but not to the summary statistics used in control charts (such as X-bar, Range, Standard Deviation and Moving Average).

For this reason specification limits can only be used with an Individuals & moving range control chart, because it includes the upper and lower Specification Limit measure objects that allow you to build a Desktop Intelligence query and plot the specification limits in a trend line chart.

Process Control Analytics (Samples)

The following samples based on the Control Chart analytic.

These samples are available at Dashboard Builder > Analytic Catalog >

Process Control Analytics Samples:

Shewhart charts for Attribute data

• c chart • u chart • u chart standardized • np chart • p chart • p chart standardized

Shewhart charts for Variable data

• X-bar & range

• X-bar & standard deviation

• Median and range

• Individuals & moving range

• Moving average and moving range CUSUM and EWMA charts

• Cusum on defects • Cusum on individuals • Cusum on x-bar • EWMA on rejects • EWMA on individuals • EWMA on x-bar Related Topics

• Control Chart analytic based on a Process Analysis Control Chart

c chart

The c chart on the Process Control Analytics tab in the Dashboard Builder Analytic Catalog is an example of a Defects (c) control chart. It monitors the number of defects, errors and accidents with a constant sample size.