WorksheetFunction.Z_Test(Object, Double, Object) Method
Definition
Important
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Returns the one-tailed probability-value of a z-test. For a given hypothesized population mean, Z_TEST returns the probability that the sample mean would be greater than the average of observations in the data set (array) — that is, the observed sample mean.
public double Z_Test (object Arg1, double Arg2, object Arg3);Public Function Z_Test (Arg1 As Object, Arg2 As Double, Optional Arg3 As Object) As DoubleParameters
- Arg1
- Object
Array is the array or range of data against which to test the hypothesized population mean.
- Arg2
- Double
The value to test.
- Arg3
- Object
Sigma - The population (known) standard deviation. If omitted, the sample standard deviation is used.
Returns
Remarks
If array is empty, Z_Test returns the #N/A error value.
Z_Test is calculated as follows when sigma is not omitted:
Figure 1: Equation for Z_Test when sigma is not omitted
or when sigma is omitted:
Figure 2: Equation for Z_Test when sigma is omitted
where x is the sample mean AVERAGE(array); s is the sample standard deviation STDEV_S(array); and n is the number of observations in the sample COUNT(array).
Z_Test represents the probability that the sample mean would be greater than the observed value AVERAGE(array), when the underlying population mean is μ0. From the symmetry of the Normal distribution, if AVERAGE(array) < μ0, Z_Test will return a value greater than 0.5.
The following Excel formula can be used to calculate the two-tailed probability that the sample mean would be further from μ0 (in either direction) than AVERAGE(array), when the underlying population mean is μ0:
=2 * MIN(Z_TEST(array,μ0,sigma), 1 - Z_TEST(array,μ0,sigma)).