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. Author manuscript; available in PMC: 2012 Oct 10.
Published in final edited form as: Neurobiol Aging. 2010 Jun 11;31(8):1263–1274. doi: 10.1016/j.neurobiolaging.2010.04.024

Table 3.

Fitted sigmoid parameters. Individual Z scores were plotted against ADAS-Cog scores and the three parameters (asym, xmid and scal) of the generic sigmoid curve (y = asym/(1 + exp((xmid-x)/scal))) were fitted using a nonlinear least square algorithm. Sigmoid was better than linear fit for CSF Aβ 1–42, tau and hippocampal volume (for the latter: sigmoid nonsignificantly better than linear); linear fitting was better for FDG-PET.

asym xmid scal R2
Tau 1.68 [1.31–2.05] 9.67 [7.72–11.62] 1.85 [0.14–3.56] 0.137
Aβ 1–42 1.26 [1.09–1.43] 8.71 [7.58–9.83] 1.40 [0.41–2.40] 0.256
FDG-PET 1.72 [1.07–2.37] 16.13 [11.16–21.09]* 4.77 [1.88–7.65] 0.201
Hippocampal volume 2.13 [1.76–2.51] 11.82 [9.98–13.66] 3.18 [1.78–4.57] 0.279

Values are fitted parameters [95% confidence interval].

*

Denotes significant difference versus all other estimated parameters.