**Public Function ZTst( _
ByRef vValues As Variant _
, ByVal vX As Variant _
, Optional ByVal vStdDev As Variant _
) As Variant**

**Returns the two-tailed P-value of a z-test. **

**Examples:** ZTst(SampleData, 140) = 1.86856876203254E-02
ZTst(SampleData, 145) = 0.47548674795769
ZTst(SampleData, 150) = 0.974926913222556

**See also:** NormalCDF Function
NormalPDF Function
NormalInverse Function
Standardize Function
ZTEST Function (Microsoft Excel)

**vValues:** Numeric-type array or Variant array containing only numeric elements. This function is NOT affected by the current setting of the StatVarType Property. It assumes that vValues is an array that contains only numeric elements.

**vX:** The value to be tested against the data in vValues.

**vStdDev:** Optional known standard deviation to be used within the cumulative distribution function. Function uses the sample standard deviation if vStdDev is missing.

**Return value:** Function returns the two-tailed P-value of a z-test. Function returns Null if the array is empty, if vX cannot be interpreted as a number, or if there is some type of error, such as if the argument is a Variant array which contains an Object reference or String. Copyright 1996-1999 Entisoft

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