Microsoft KB Archive/123196

= Microsoft Knowledge Base =

XL: P(Z<=z) Values Reversed in z-Test: Two Sample For Means
Last reviewed: December 17, 1996

Article ID: Q123196

The information in this article applies to:


 * Microsoft Excel for Windows, versions 5.0, 5.0c
 * Microsoft Excel for the Macintosh, versions 5.0, 5.0a
 * Microsoft Excel for Windows 95, versions 7.0, 7.0a

SYMPTOMS
In Microsoft Excel, when you use the z-Test: Two-Sample For Means statistical tool to return information about your data, the P(Z<=z) two-tail value is incorrect.

CAUSE
When you use the z-Test: Two-Sample For Means tool to analyze your data, the value returned for the P(Z<=z) two-tail should be twice the value returned for P(Z<=z) one-tail. However, in the versions of Microsoft Excel listed above, the P(Z<=z) two-tail value returned is incorrect.

STATUS
Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was corrected in Microsoft Excel 97.

MORE INFORMATION
You can use the z-Test: Two-Sample For Means to perform a two-sample z- test for means with known variances on your data. This tool is available by clicking Data Analysis on the Tools menu in Microsoft Excel, when the Analysis ToolPak add-in is loaded. The Analysis ToolPak file (Analysis.xll for version 5.0 and Analys32.xll for version 7.0) is located in the Library\Analysis folder in your Microsoft Excel folder.