CONFIDENCE.NORM and CONFIDENCE in ONLYOFFICE Spreadsheet Editor

• Introduced: Original introduction release is not established by the sources checked.
• Available: Documented in current unversioned ONLYOFFICE function help, checked October 18, 2026.
• Implementation inspected: Official SDKJS v10.0.0.169, commit 3679e0375a758d7dc59d31337a45461be3525ed8. This establishes a source snapshot, not identical behavior in every installed editor.
• Retired or deprecated: Retirement or formal deprecation is not established by these sources. A legacy spelling is not automatically a removed function.
• Testing: Examples are independently calculated or labeled source predictions. No ONLYOFFICE application or calculation-engine execution was performed. No native screenshot or general import/export guarantee is claimed.

Use English names and comma separators as shown; adapt separators outside quoted text if your locale requires semicolons. Keep full precision in calculations and round only the displayed summary.

=CONFIDENCE.NORM(alpha, standard_dev, size)

Exactly three arguments are registered. The function does not accept a mean and does not return a pair of endpoints. Its output is the margin, or half-width, of the usual symmetric interval. Full interval width is twice that number.

The normal-based calculation uses z(1−alpha/2) × sigma / sqrt(n). Its classical mean-interval interpretation uses a known population standard deviation and a suitable normal or normal-approximation model. The calculation does not validate those assumptions from the three numbers supplied.

NIST’s confidence-interval explanation distinguishes a known population sigma from an estimated standard deviation.

Suppose a measurement model uses known population standard deviation 2, sample size 100, and a sample mean of 10. The standard error is 2/sqrt(100)=0.2.

1. Put alpha 0.05 in A2, standard deviation 2 in B2 and size 100 in C2.
2. Enter =CONFIDENCE.NORM(A2,B2,C2) in D2.
3. The independent half-width is 0.391992796908.
4. Put the mean 10 in E2, then compute =E2-D2 and =E2+D2: approximately 9.60800720309 and 10.3919927969.

The standard normal 97.5th percentile is approximately 1.95996398454. Multiplying it by standard error 0.2 gives the half-width. The legacy =CONFIDENCE(0.05,2,100) follows the same inspected calculation method.

These are independently reasoned values. A displayed interval does not establish that the claimed population standard deviation is known or that the sample was collected appropriately.

A 95% two-sided interval uses alpha 0.05, not 0.95. The critical point is based on alpha/2 in each tail. Decreasing alpha asks for higher confidence and generally widens the interval; increasing the standard deviation also widens it.

The returned half-width has the same units as standard_dev. If the measurements are in seconds, the margin is in seconds, not a percentage. Formatting the margin as a percentage does not convert it into a confidence level.

For a fixed normal critical value and standard deviation, quadrupling sample size from 100 to 400 halves the margin: 0.195996398454. This follows from the square-root denominator, not a linear 1/n rule. If standard deviation is estimated rather than known, changing n can also affect which reference distribution is appropriate.

A confidence interval for a mean is not a prediction interval for one future observation. Nor does a computed 95% interval establish a 95% posterior probability for a fixed parameter without an appropriate probabilistic framework. The spreadsheet computes a standard formula; interpretation depends on the sampling model.

The implementation rejects alpha at or outside 0–1, standard_dev at or below zero and size below 1 after integer parsing, using the numeric-error category, conventionally #NUM!. The table’s error is a source prediction rather than an application observation. Size is parsed as an integer, so enter the actual whole sample count rather than relying on fractional truncation.

The normal formula accepts n=1 at the source guard when a positive standard deviation is supplied. That does not prove the statistical assumptions or the provenance of sigma. Text conversion, embedded errors and array behavior can produce additional outcomes not established by the scalar examples.

These are independent mathematical expectations or identified source-error predictions, not native application results. Preserve full input precision when reproducing them.

The legacy name CONFIDENCE is covered in this guide. The modern name inherits CONFIDENCE’s calculation method. This source relationship does not establish identical metadata, file serialization or every imported-workbook behavior. Legacy does not by itself mean formally deprecated or removed.

Use the exact probability direction, parameter order and data meaning above when moving a workbook between products. Similar names are not a general cross-version or file-format compatibility guarantee.

AVERAGE calculates a sample mean; COUNT counts numeric observations; SQRT exposes the standard-error calculation.

• Official CONFIDENCE.NORM help, checked October 18, 2026.
• Pinned SDKJS implementation, including parameter validation and numerical helpers.
• Official CONFIDENCE help.