ZTEST in WPS Spreadsheet: Interpret a One-Tailed z-Test

With values 9,10,10,11 in A2:A5, =ZTEST(A2:A5,9,2) has an independent expected result of 0.158655253931. The sample mean is 10, the hypothesized mean is 9, and the specified population standard deviation is 2. The output is the upper-tail probability under that null model, not the chance that the null mean is true.

ZTEST(array,μ0,[sigma])

Square brackets mark an optional argument and are not typed into the formula. The WPS lesson’s first syntax line omits brackets, but its localized syntax and argument description explicitly make sigma optional; this guide displays that documented optionality. array is the required numeric sample range or array; μ0 is the required numeric hypothesized population mean; sigma is the optional known population standard deviation. Use an explicitly positive sigma in the initial example. If sigma is omitted, the documented default is the sample standard deviation. The μ0 symbol denotes the argument’s role; in a formula, supply a number or cell reference there.

Enter 9,10,10,11 in A2:A5. Put 9 in C2 and 2 in C3, labeled Null mean and Known population standard deviation. Enter =ZTEST(A2:A5,C2,C3) in E2. Expect approximately 0.158655253931 under the documented probability convention.

Independently, n=4 and the mean is 10. The standard error is sigma/√n=2/2=1, and z=(10−9)/1=1. The upper standard-normal tail is 1−Φ(1)=0.158655253931. This equation is an independent mathematical interpretation, not a report of WPS execution.

Keeping the same data and sigma, =ZTEST(A2:A5,10,2) is independently expected to give 0.5. Changing the null mean to 11 gives 0.841344746069: the observed mean is now below the null, so the upper-tail result exceeds 0.5.

The worksheet lesson’s first sentence is awkward about direction. WPS’s separate Open Platform ZTest method documentation explicitly says the result exceeds 0.5 when the observed mean is below μ0, and supplies a two-tail transformation. That corroborates the upper-tail reading; an automation-method page does not independently establish every worksheet build’s behavior.

If E2 contains the one-tail result, use:

=2*MIN(E2,1-E2)

For the first example, expect 0.317310507863. Simply doubling E2 would be wrong when E2 exceeds 0.5. The symmetric minimum uses the smaller tail before doubling. For an explicitly lower-tail alternative, 1−E2 is the complementary probability, but choose the hypothesis before seeing which tail is small.

Omitting sigma requests the sample-standard-deviation substitution, not a Student t-test. In the teaching sample, the sample standard deviation is √(2/3), giving z=√6 for null mean 9 and an independent normal-tail expectation of about 0.007152939218. This large change illustrates why known population spread and estimated sample spread must not be substituted casually. Unknown-variance inference, especially with small samples, often calls for a t-based analysis justified separately.

Use consistent measurement units for observations, null mean and sigma. Sigma is a standard deviation, not variance or standard error. With omitted sigma, use at least two valid observations and nonzero sample spread for the mathematical calculation. The Open Platform source documents #N/A for an empty array; other exact worksheet error codes for invalid sigma or degenerate data are not established here.

A right-tail p-value near one can be expected when the observed mean is below the null; it is not automatically a formula failure. A valid probability also does not validate random sampling, independence, a normal approximation or the claim that sigma is truly known. No introduction or retirement build is established by the sources.

The official WPS ZTEST lesson was checked on October 19, 2026. Its edition banner identifies WPS Office for Windows Personal. This Chinese first-party documentation is not proof of universal English-global, Mac, Linux, web or mobile support. Introduction and retirement versions remain unknown. All numerical results in this guide are independently calculated expectations, not native WPS test results or borrowed Excel outputs. Current GUI access was unavailable; no current-application screenshots or native execution are claimed.

Direction is additionally corroborated by the WPS Open Platform ZTest method documentation, checked on the same date; its method/API scope is separate from the worksheet lesson.

AVERAGE, MIN, STDEV.S. Browse the WPS function library.