Technical Comments

Comment on “Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581”

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Science  06 Mar 2015:
Vol. 347, Issue 6226, pp. 1080
DOI: 10.1126/science.1260796


  • Fig. 1

    This example illustrates why residual statistics must not be used to assess significance in multiparametric fits to data. We want to know if a constant x0 is needed to model the position x of a body as a function of time t (black dots). (A) (Top) represents the fit to the null hypothesis (model A), which only includes a velocity term (red line). (A) (Bottom) shows the residuals rA= x – xA(t) to model A. An attempt to fit a model with a constant offset to rA is shown as a red line. (B) (Top) represents a fit adjusting all the parameters simultaneously (model B, top right panel, blue line), producing the largest possible reduction in χ2.

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