Counted attribute characteristic settings

Counted attribute characteristics are measured by using integer numbers.

If you selected Counted attribute in the Characteristic Type menu, then provide the following information:

Sample Size Source

Specifies how the sample size is determined for the attribute. The values are as follows:

• Fixed

  Specifies the fixed sample size value in the normal sample size property.

• Entered

  Enables the option to set the minimum and maximum data entry limits for the sample size.

• Copied from previous

  Specifies the same value that is entered. At run time, the Sample Viewer .Net control resets the sample size to the value that was previously saved for the characteristic. This value uses the minimum and maximum sample size properties to set the data entry limits.

Number of Defect Opportunities

This field is enabled for counted attributes. You must enter the number of possible defects on a single unit. For example, if a unit is inspected for a defect on each face of a box with one defect allowed per face, then the number of defect opportunities is 6.

Note: The optional information for defining an attribute type characteristic are defect opportunities and control limits for preset values. If the optional information is of a counted attribute type, then you must set the number of defect opportunities.

Control Limit Source

You can obtain Control Limits in the following ways:

• Automatically Calculate from Data

  Allows MES to calculate the control limits. This enables the options to enter the following:

  • Samples for Control Limit: Specifies the number of samples that are to be included in the calculation. This parameter limits the number of samples used in the calculation of control limits and process statistics, as do the parameters Cut-off time (in days) and Number of samples to consider calculating process statistics. For more information, see Control the amount of data used in process statistics calculations.

  • Samples required before Control Limits are calculated: Specifies the minimum number of samples that must exist before applying the calculated control limits to evaluate rule violations.

• Compute from standard values

  Specifies standard mean and standard deviation values, which are used to calculate control limits adjusted for sample size. This includes the following:

  • Standard Average Number per Unit: (Center Line) includes c, u, and DPMO charts. Enter the value as a count per unit. For example, if you take 20 samples and enter the standard average number per unit as 5, then a c chart of the data would have a center line at 100.

  • Standard Average Number per Unit Is Target, if selected, indicates that the target is used as the Center Line for the standard average number per unit and the standard average number per unit of the characteristic is not used.

• Use preset values

  Includes center line and upper and lower control limit values for c and u charts. DPMO charts use the same settings as the u chart and are scaled accordingly. Enables the user to set control limits for each chart through the Chart and its limits list. For each chart component, you must enter the lower control limit, center line, and upper control limit.

  Select the Use preset values option to enter values for all the chart types.