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Interactive application of quadratic expansion of chi-square statistic to nonlinear curve fittingThis report contains a detailed theoretical description of an all-purpose, interactive curve-fitting routine that is based on P. R. Bevington's description of the quadratic expansion of the Chi-Square statistic. The method is implemented in the associated interactive, graphics-based computer program. Taylor's expansion of Chi-Square is first introduced, and justifications for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations is derived, then solved by matrix algebra. A brief description of the code is presented along with a limited number of changes that are required to customize the program of a particular task. To evaluate the performance of the method and the goodness of nonlinear curve fitting, two typical engineering problems are examined and the graphical and tabular output of each is discussed. A complete listing of the entire package is included as an appendix.
Document ID
Document Type
Technical Memorandum (TM)
Badavi, F. F.
(PRC Kentron, Inc. Hampton, Va., United States)
Everhart, Joel L.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 5, 2013
Publication Date
October 1, 1987
Subject Category
Statistics And Probability
Report/Patent Number
NAS 1.15:4012
Accession Number
Funding Number(s)
PROJECT: RTOP 505-60-21-01
Distribution Limits
Work of the US Gov. Public Use Permitted.
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