Microsoft KB Archive/158071

= Problems vith Statistical Functions and Large Numbers in Excel =

Article ID: 158071

Article Last Modified on 6/12/2007

-

APPLIES TO


 * Microsoft Office Excel 2003
 * Microsoft Excel 2002 Standard Edition
 * Microsoft Excel 2000 Standard Edition
 * Microsoft Excel 97 Standard Edition
 * Microsoft Excel 95 Standard Edition
 * Microsoft Excel 95a
 * Microsoft Excel 5.0 Standard Edition
 * Microsoft Excel 5.0c
 * Microsoft Excel 2004 for Mac
 * Microsoft Excel 2001 for Mac
 * Microsoft Excel 98 for Macintosh
 * Microsoft Excel 5.0 for Macintosh
 * Microsoft Excel 5.0a for Macintosh

-



This article was previously published under Q158071





SYMPTOMS
In Microsoft Excel, when you use any of the following statistical functions in a formula:

STDEV

STDEVP

LINEST

LOGEST

KURT

NEGBINOMDIST

BINOMDIST

The formula may return an incorrect result.



CAUSE
This behavior may occur when the formula refers to very large numbers that, when summed, multiplied, or squared, exceed 15 digits in length.



MORE INFORMATION
Microsoft Excel supports a maximum of 15 significant digits at all times. This limit applies to a value that is calculated by a formula. Because of this limitation, if at any time a formula calculates a value that exceeds 15 digits in length, digits beyond the fifteenth significant digit are changed to zeroes. This may cause the formula to return an incorrect result.

For example, when you use the STDEV function to calculate the standard deviation of a set of numbers, part of the function sums the numbers and then squares the result. If this number exceeds 15 digits in length, digits beyond the fifteenth digit are changed to zeroes. This affects the final result delivered by the formula. To see an example of this behavior, enter the following data in a worksheet:   A1: 999999          B1: 99999999 A2: 1000000        B2: 100000000 A3: 1000001        B3: 100000001 A4: =STDEV(A1:A3)  B4: =STDEV(B1:B3) Although both formulas return the same standard deviation, 1, the second formula returns a zero. Because the square of the sum of the three values in B1:B3 is greater than 15 digits in length, digits beyond the fifteenth digit are changed to zeroes. This causes the formula to return an incorrect result.

This behavior may occur when you use any of the statistical functions listed in this article and you work with very large values. This is true because these functions all use squared values, which makes it probable that the limit of 15 significant digits is exceeded.

The exact formulas used by functions in Microsoft Excel are listed in the Help topic for each function in Microsoft Excel Help.

