Parameter Bias Uncertainty Worksheet Features 
The Parameter Bias Uncertainty Worksheet is useful for entering parameter specifications. This worksheet is activated by clicking Tolerance Limits on the Main Screen menu.  Worksheet functions and features are described below.

Menu Bar

Worksheet entries are accepted and the worksheet closed by selecting OK on the menu.  Conversely, new entries or changes are ignored and the worksheet closed by selecting Cancel on the menu.  Worksheet entries can be cut, copied, pasted, or deleted via the Edit menu.

Selecting Run on the menu opens the Run External Application Screen, which can be used to launch external Windows applications from within AccuracyRatio.  Selecting Reliability from the menu opens the Reliability Model Worksheet, which is used to model the change in in-tolerance probability with time of measurement and test equipment.  Once the reliability behavior for the subject and/or measuring parameter has been modeled, the in-tolerance probability at any time elapsed since measurement can be calculated using the % In-Tolerance Reference Screen, which is activated by selecting Bias Reference on the menu.

Tool Bar

The Tool bar provides icons that can be used to access selected options and functions.  A brief description of the associated function or options can be obtained by placing the mouse cursor over the icon of interest.

Mode Value and Measurement Units

In this section of the worksheet, the measurement area and corresponding units are selected from drop-down lists and the nominal or reading value entered.   Once the measurement area, units and nominal value have been established, the worksheet is ready for entering the tolerances for the subject parameter and the measuring parameter. 

Subject Parameter Tolerances

Tolerance limits can be entered as two-sided, two-sided symmetric, single-sided upper or single-sided lower values. If the Single-Sided Upper option is selected for the subject parameter tolerance option, the Lower Tolerance Limit box is replaced with a Physical Limit box. If the Single-Sided Lower option is selected, the Physical Limit box replaces the Upper Tolerance Limit box. The physical limit is a design constraint or physical limitation on the subject parameter.

 
If you select either the single-sided upper or lower option and can make a fair guess at the subject parameter's physical limit, select the Yes option under Input Physical Limit. If you can't estimate a physical limit, or if one does not apply, select the No option.  If you select the No option, AccuracyRatio will assume there is no physical limit for the subject parameter. 

Tolerances can be computed as a linear combination of a fixed value and % of nominal or reading.  Tolerance units are selected from a drop-down list.  The subject parameter bias uncertainty is then automatially computed when a specified % In-tolerance is entered.  The subject parameter % In-tolerance is an estimate of the probability that the parameter is in-tolerance at the time of measurement. This value may be entered directly or determined using the Reliability Model Worksheet and the % In-Tolerance Reference Screen.

Measuring Parameter Tolerances
Two-sided symmetric tolerance limits can be computed as linear combination of a fixed value and % of nominal or reading.  Tolerance units are selected from a drop-down list.  The measuring parameter bias uncertainty is then automatially computed when a specified % In-tolerance is entered.    
 

Alternatively, if the Error Containment Limits / Uncertainties option had been selected for the measuring parameter, you may enter either an Expanded Uncertainty or a Bias Uncertainty directly.  The expanded uncertainty serves as a confidence limit for the bias uncertainty.  This limit is sometimes called an "error containment limit." The expanded uncertainty and bias uncertainty are related through the Coverage Factor or the Confidence (%) level.  The relationship is influenced by the Degrees of Freedom.
 
Parameter Bias Distributions
Plots of the statistical distributions for the subject parameter bias and measuring parameter bias can be viewed by selecting either Subject Parameter Bias Distribution or Measuring Parameter Bias Distribution from the Plots menu.