# Difference between revisions of "Documentation/SL/How Tos/Calc: funkcija ZTEST"

## ZTEST

Vrne rezultat z-preizkusa.

ZTEST(podatki; μ; σ)

podatki is a range or array containing a random sample from a population (population assumed to have a normal distribution).
μ je (znana) srednja vrednost populacije.
σ je znani standardni odklon celotne populacije. Če tega argumenta ni, bo ocenjen iz vzorčnih podatkov z STDEV(podatki).
ZTEST izračuna z-statistiko:
kjer je m je sample srednja vrednost in n število v vzorcu. Če sta srednja vrednost in standardni odklon populacije znana, z-statistika forms a standard normal distribution - that is, a normal distribution s srednjo vrednostjo=0 in standardnim odklonom=1.
ZTEST vrne one-sided cumulative probability - the area under the standard normal curve to the right of the z value (shaded blue here):

### Example:

ZTEST(A2:A20; 9; 2)

returns the result of a z-test on a sample A2:A20 drawn from a population with known mean 9 and known standard deviation 2.

### Issues:

• Excel has referred to this as both a one-tailed and a two-tailed test. Neither is correct - the test is one-sided as described above. For example when z = -1.5 part of the left tail and all of the right tail are included. This is an unconventional measure, but can be used.
• Calc has produced incorrect results for the 3 parameter version of this function. See issue 90759.
• As with all statistics, a good understanding is needed for reliable results.