Retrieval/Configuration settings for SPC retrievals

The Retrieval/Configuration node on the Settings tab offers multiple options for changing the GainSeeker default retrieval settings on all SPC chart types, including statistics lists, multiple charts, and data tables. Information about each of these settings is featured in this topic.

 

Contents  [Hide]

 

You can choose default settings for charts in the GainSeeker System Administration module. See Chart Defaults settings

Navigating to these settings

The Retrieval/Configuration node is located at the top level on the Settings tab:

For help with using tree structures like the one on the Settings tab, see Navigating Tree Structures

Conversion multiplier

Each standard is configured for a particular measurement unit such as inches or kilograms. You can report data and statistics using a different measurement unit. Measurement system conversion does not change any of the data stored in GainSeeker. It only changes the numbers that display when charts and reports are drawn.

  1. Double-click Conversion multiplier = on the Settings tab to open the Data Conversion dialog.

  2. On Data Conversion, click Examples... to view the list of Common conversions.

  3. Click a conversion in the list, and then click Paste. The selection will display on the Data Conversion dialog.

Creating your own conversion multiplier list

You can create your own conversion multiplier list if the current list of Common conversions does not meet your requirements. Note that any new list you create replaces the existing Common conversions list, but you can add any existing conversions to the new list you create.

To get started:

  1. Click the Help menu option on the GainSeeker Charts module

  2. Then, click About in the menu to open About GainSeeker Charts.

  1. Use the scrollbar on About GainSeeker Charts to locate the path on your computer to the Settings path: (Make note of the path for use in step 4.)

  1. Open Windows Explorer on your computer. Use the path you noted in step 3 to locate the settings folder.

  2. Open the settings folder, and then right-click to display the right-click menu. From the menu, select New. From the submenu that opens, select Text Document.

  3. Name the new file convert.txt and then open the file to edit it.

  4. Enter a new conversion in the convert.txt file using this syntax:

Unit_2 = Unit_1 * number

  1. Add any additional conversions you want on a new row using the syntax shown in step 7.

Any conversions listed in the convert.txt file will now display as options in the Common conversions list field.

CuSum/Control charts

Acceptance limit based on

The acceptance limit is used to calculate the upper and lower CuSum values for each data subgroup. When performing real-time CuSum checks, the upper and lower CuSum values for the data subgroup are checked against the acceptance limit. The acceptance limit can be based on the Upper Ind. Gate, the Upper Gate, or the Upper Spec from the standard for which data is being charted.

Decision interval value =

This value is used to calculate the upper and lower CuSum value for data subgroups.

Start value constant =

This value is used to calculate the upper and lower CuSum value for a data subgroup when that subgroup is the first in the data set retrieved. It is also used in the upper or lower CuSum calculation when the previous CuSum value exceeded the acceptance limit.

More information

EWMA weight =

Select the weighting factor for EWMA charts. A typical factor is 0.15 .

To configure this value, double-click EWMA weight, and then enter a numeric value on the Enter Value dialog that opens.

Group data on Control and CuSum charts =

Double-click the Group data on Control and CuSum charts = setting to open the Group SPC Data dialog. See Grouping SPC Data for information about the Group data by options.

Method for calculating control limits

Choose a standard deviation method for calculating control limits. The Factors (R-bar / d2) method provides the best prediction if your data exhibits more variation within subgroups than between subgroups. The Sample standard deviation method provides the best prediction if your data exhibits more variation between subgroups than within subgroups.

For information on changing the default setting, see SPC Statistics.

Method for calculating standard deviation

Choose a method for calculating standard deviation for other statistics. The Factors (R-bar / d2) method provides the best prediction if your data exhibits more variation within subgroups than between subgroups, while the Sample standard deviation method provides the best prediction if your data exhibits more variation between subgroups than within subgroups.

The method you choose will be used to calculate the Mean +/- 3SD, Mean +/- 4SD, 6SD, Zl, Zu, and Cpm for data in a normal distribution.

Moving average span =

This number represent the number of data points that will be averaged for Moving Average charts.

To configure this value, double-click Moving average span and then enter the a numeric value greater than 1 in the Enter value dialog that opens.

Non-normal

To configure settings for how SPC should work with data that is non-normally distributed, expand the Non-normal node.

The setting options:

Calculate non-symmetrical control limits for subgroup size = 1

GainSeeker can calculate non-symmetrical control limits if the subgroup size is one and the distribution is non-normal, but can be modeled. This option is selected by GainSeeker by default. For more information on non-symmetrical control limits, see Non-symmetrical control limits.

Evaluate more data sets as non-normal

If this option is selected, GainSeeker uses 95% or 99% percent confidence limits to determine normality of data.

Force distribution

Select an option for analyzing the normality of a data distribution:

Limit number of slices for non-normal area calculation

You can choose unlimited non-normal slices or limited non-normal slices at 2048. The larger the number of slices, the longer the program will take to calculate non-normal area for unusual distributions. This option is selected by GainSeeker default.

Use the median method to calculate Z values instead of probability method

GainSeeker calculates Z values using the median method instead of the probability method if this option is selected. This option is selected by GainSeeker default.

Retrieve data =

Double-click Retrieve data = to open the Retrieve Data dialog.

For example, when analyzing 25 data records and each record has a subgroup size of 3, then each subgroup will be broken up into 3 data records with one measurement each. The result will be data analysis for 75 data records with a subgroup size of 1.

For example, if you choose to retrieve the third column when analyzing 100 data subgroups, the result will be data analysis for 100 data points with a subgroup size of 1.

Run length =

The number of consecutive points needed to identify a run or a trend can be set to 6, 7, or 8. The GainSeeker default setting is 7.

To change this setting, double-click Run length= and enter 6, 7, or 8 in the text box of the Enter Value dialog that opens.

Run values based on

Choose whether to calculate mean and zone based on Control or Gate limits for real-time checks on runs, trends, and zones (points outside 1SD or 2SD).

For information on changing the default setting, see SPC Data Entry.

Show time to

To set the precision for displaying time stamps, expand Show time to and select an option.

For information on changing the default setting, see Calendar and dates

Statistical outliers

Expand Statistical outliers and select which data to include. Statistical outliers are observations that violate SPC rules.

If you choose to exclude statistical outliers, the out-of-control data points will be displayed as outliers on control charts and data tables, but will be excluded from the statistical calculations.

For information on changing the default setting, see SPC Statistics.

Note about excluding outliers and occasional oscillation cycle occurrences:

When you choose to exclude outliers, GainSeeker loops through the data at least twice to determine if excluding the outliers will change the control limits to a point that will push other data points outside the new control limits, creating new outliers. Typically, the outlier loop is only executed a few times, however, there are times when the outliers endlessly oscillate in and out of control limits. This can happen when control limits change as data points are excluded/included on subsequent passes through the data set. Thus, GainSeeker is limited to a maximum ten passes when such an oscillation cycle occurs.

Trend chart limits

If your report includes the statistic "Trend crosses at," which returns the x value where the trend line is expected to cross the closest limit on a trend chart of the retrieved data, that statistic will be affected by the limits selected here.

Varying subgroup size =

To configure the settings for incomplete subgroups and varying subgroup sizes, double-click Varying subgroup size to open the Incomplete Subgroups and Varying Subgroup Sizes dialog:

Each time you retrieve data for a standard, GainSeeker will count the number of measurements stored for each subgroup in the retrieval. If you retrieved data with incomplete subgroups or multiple subgroup sizes, the number of measurements per-subgroup will not be identical for all subgroups in the retrieval. GainSeeker will use these settings to determine how statistics will be calculated on this data:

If more than n percent of the subgroups in this retrieval also contain this number of measurements, then any subgroups that do not contain this number of measurements will be displayed on charts and data tables, but temporarily excluded from statistical calculations.

If the number of subgroups in this retrieval is less than or equal to the percentage you specify here, GainSeeker will not use this setting to exclude data from statistical calculations. Instead, it will proceed according to the options you have configured for options 3. and 4. described below.

DFi = Degrees of Freedom for subgroup number i

DF = Degrees of Freedom for the subgroups being analyzed

k = the number of subgroups being analyzed

DF = DF1 + DF2 + ... + DFk

GainSeeker will count the number of measurements stored for the most recent subgroup in the retrieval. It will then calculate the degrees of freedom for subgroups in the retrieval that contain this number of measurements:

If the subgroups containing this number of measurements provide more than n degrees of freedom, any subgroups that do not contain this number of measurements will be displayed on charts and data tables, but temporarily excluded from statistical calculations.

If the subgroups containing this number of measurements do not provide more than n degrees of freedom, GainSeeker will not use this setting to exclude data from statistical calculations. Instead, it will proceed according to the options you have configured for option 4. below.

For information on changing the default setting, see SPC Statistics.