Appendix Figure. Conversion Model Illustration.

Illustration of the idea that there is not one conversion model with fixed parameters but a distribution of models. In practice, when a CSF Aβ value is converted to PIBcalc, a number of PIBcalc values will be generated based on this distribution of models. Each distribution shown above is centered at the least squares estimates with a standard deviation approximately equal to the standard error from the least squares fit. The intercept which we denote by β₀ has a distribution centered at the least squares estimate of 5.326. Similarly, the CSF Aβ (β₁) and the APOE (β₂) coefficients will the centered at -0.615 and 0.184. The differences in the standard errors among the coefficients are reflected in the differences in the heights and widths of the distribution curves. The error term (e) will be centered at 0 with a standard deviation of approximately 0.180, the residual standard error from the least squares fit.