Determination of the Uncertainties in S-Curve Logistic Fits

Theodore Modis

No n53pd, OSF Preprints from Center for Open Science

Abstract: Look-up tables and graphs are provided for determining the uncertainties during logistic fits, on the three parameters M, α and to describing an S-curve of the form: S(t) = M/(1+exp(-α(t-t0))). The uncertainties and the associated confidence levels are given as a function of the uncertainty on the data points and the length of the historical period. Correlations between these variables are also examined; they make “what-if” games possible even before doing the fit. The study is based on some 35,000 S-curve fits on simulated data covering a variety of conditions and carried out via a χ2 minimization technique. A rule-of-thumb general result is that, given at least half of the S-curve range and a precision of better than 10% on each historical point, the uncertainty on M will be less than 20% with 90% confidence level.

Date: 1994-05-31
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Citations: View citations in EconPapers (14)

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Persistent link: https://EconPapers.repec.org/RePEc:osf:osfxxx:n53pd

DOI: 10.31219/osf.io/n53pd

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