Article ID: 828313  View products that this article applies to. On This PageSUMMARYThis article describes the CHIINV function in Microsoft
Office Excel 2003 and in later versions of Excel and discusses an improvement in Excel 2003 and in later versions of Excel that can affect
results in extreme cases when compared with earlier versions of
Excel. MORE INFORMATIONCHIINV(p, df) is the inverse function for CHIDIST(x, df).
For any particular x, CHIDIST(x, df) returns the probability that a
ChiSquaredistributed random variable with df degrees of freedom is greater
than or equal to x. The CHIINV(p, df) function returns the value x where CHIDIST(x, df) returns p. Therefore, CHIINV is evaluated by a search process that returns the appropriate value of x by evaluating CHIDIST for various candidate values of x until it finds a value of x where CHIDIST(x, df) is "acceptably close" to p. Syntax
Example of usageTo illustrate the CHIINV function, create a blank Excel worksheet, copy the following table, select cell A1 in your blank Excel worksheet, and then paste the entries so that the table fills cells A1:F21 in your worksheet.Collapse this table
Note 1 This example comes from the long out of print text: Bell, C.E., Quantitative Methods for Administration, Irwin, 1977. Results in earlier versions of ExcelCHIINV(p, df) is found through an iterative process that repeatedly evaluates CHIDIST(x, df) and returns a value of x such that CHIDIST(x, df) is "acceptably close" to p. Therefore accuracy of CHIINV depends on the following factors:
Results in Excel 2003 and in later versions of ExcelNo changes were made to CHIDIST in Excel 2003 and in later versions of Excel. The only change that affects CHIINV was to redefine "acceptably close" in the search process to be much closer. The search now continues until the closest possible value of x is found (in the limits of Excel's finite precision arithmetic). The resulting x should have a CHIDIST(x, df) value that differs from p by about 10^(15).ConclusionsMany inverse functions have been improved for Excel 2003 and for later versions of Excel. Some have been improved for Excel 2003 and for later versions of Excel only by continuing the search process to gain a higher level of refinement. This set of inverse functions includes the following functions: BETAINV, CHIINV, FINV, GAMMAINV, and TINV.No modifications were made to the respective functions that are called by the following inverse functions: BETADIST, CHIDIST, FDIST, GAMMADIST, and TDIST. Additionally, this same improvement in the search process was made for NORMSINV in Microsoft Excel 2002. For Excel 2003 and for later versions of Excel, accuracy of NORMSDIST (called by NORMSINV) was improved also. These changes also affect NORMINV and LOGINV (these call NORMSINV) and NORMDIST and LOGNORMDIST (these call NORMSDIST). PropertiesArticle ID: 828313  Last Review: January 18, 2007  Revision: 2.2

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