Previous Topic

Next Topic

Book Contents

Book Index


The z-score is the number of standard deviations a control result is from the expected mean. Use the following formula to calculate the z-score:

A z-score of 2.3 indicates the observed value is 2.3SD away from the expected mean. A data point with this z-score violates the 12s rule, but not the 13s rule. The z-score appears on the Single Test Point Data Entry dialog box.

See Also

Useful Statistics


Standard Deviation (SD)

Calculating a Control Mean and Range

Standard Deviation Index (SDI)


Coefficient of Variation (CV)

Determining an Acceptable CV

Coefficient of Variation Ratio (CVR)

Total Error (TE) and Total Allowable Error (TEa)