CM4D has a set of variables that report on different aspects of Range of Variation (ROV). These variables are the ROV Center, ROV Spread, and ROV Target variables which are described below. These variables report on the row or entire DataSet and consider only valid rows. For ROV, a row is considered NOT valid when it has no valid cell values or has no defined tolerance (or a tolerance of zero) and the high value, low value, mean, and range values are all equal to zero.
Refer to the topic DataSet Properties - Statistics Tab for more information on using multiple ROV values in a DataSet.
Tolerance is calculated depending on the type of limits available:
· Bilateral: upper limit – lower limit
· Unilateral upper: upper limit – nominal
· Unilateral lower: nominal – lower limit
To use the ROV variables the DataSet property for range of variation tolerance percentage needs to be set. This value will default to 50 percent. CM4D will refer to this value as the ROV percent value that can be reported with the CM4D variable ~rovpercent~ and herein after referred to as ROV%. An ROV% value of 50 represents 50 percent of the tolerance which can be expressed in the following equation: tolerance*(50/100).
To understand how the ROV variables work consider the following diagram with the descriptions below.
ROV Center is considered acceptable when the mean for a DataSet row falls within a target range of variation as centered on the nominal and defined by the provided ROV%. In the above example case 1, 2, 3, and 5 would be acceptable.
· Equation for the entire DataSet ROV Center: (acceptable count/valid rows)*100
· DataSet ROV Center is reportable with the variable ~DataSet,rovcenter~
· Row ROV Center is reportable with the variables: ~rovcenter~ or ~rovcenterok~
ROV Spread is considered acceptable when the range for a DataSet row is less than the target range of variation defined by the provided ROV%. In the above example case 1, 3, and 4 would be acceptable.
· Equation for the entire DataSet ROV Center: (acceptable count/valid rows)*100
· DataSet ROV Spread is reportable with the variable: ~DataSet,rovspread~
· Row ROV Spread is reportable with the variables: ~rovspread~ or ~rovspreadok~
ROV Target is considered acceptable when the mean for a DataSet row falls within a target range of variation as centered on the nominal and defined by the provided ROV% and the range for a DataSet row is less than the target range of variation defined by the provided ROV% and the range falls within the target range as centered on the nominal. In the above example only case 1 would be acceptable.
· Equation for the entire DataSet ROV Center: (acceptable count/valid rows)*100
· DataSet ROV Target is reportable with the variable: ~DataSet,rovtarget~
· Row ROV Target is reportable with the variables: ~rovtarget~ or ~rovtargetok~
~dataset,rovcenter~
Returns the ROV Center for the entire DataSet. See also, DataSet Range of Variation.
~dataset,rovspread~
Returns the ROV Spread for the entire DataSet. See also, DataSet Range of Variation.
~dataset,rovtarget~
Returns the ROV Target for the entire DataSet. See also, DataSet Range of Variation.
~rovcenter~
Returns the default ROV Center value.
~rovspread~
Returns the default ROV Spread value.
~rovtarget~
Returns the default ROV Target value.
~rovcenterok~
Returns status of the ROV Center for the row, OK or NOTOK.
~rovspreadok~
Returns status of the ROV Spread for the row, OK or NOTOK.
~rovtargetok~
Returns status of the ROV Target for the row, OK or NOTOK.