ZTEST

**Syntax:** **ZTEST( Range, X[, S])**

*Range* = a range containing sample values

*X* = a value to be tested

*S* = (optional) the standard deviation of the sampled
population, if known

**ZTEST** returns the Z-score for a two-tailed test
of the hypothesis that *X* is the mean of the population
from which the samples in *Range* are drawn. The population
is assumed to be normally distributed with standard deviation
*S*. If *S* is omitted, it is estimated from the
sample values in *Range*. If *S* is given, it must
be greater than 0.

The mathematical formulation is given as follows:

Let *z* =
, where is
the actual mean, *N* is the number of samples, and
is the standard deviation. Then,

**Examples:**

Suppose A1..A10 contains the sample values 0.552, 5.090, 4.494, 7.833, 7.101, 0.590, 2.439, -3.197, 8.861, and -2.795.

**ZTEST**(A1..A10, 3) = 0.47151484

**ZTEST**(A1..A10, 3, 4) = 0.46949987

**ZTEST**(A1..A10, 3, 0) = Error

**Excel function:** ZTEST

Grey Trout Software

02 March 2003