Probability Methods for Cost Uncertainty Analysis, 2nd Edition

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351 Building Statistical Cost Estimating Models

could be used to nd the parameters a and b that minimizes the

log-space standard error.

Figure 10.4 is a scatterplot of observations that exhibit additive

error and multiplicative error trends. In practice, it is always best

to visually examine a dataset (when possible) for its error prole

before considering the regression approach and candidate linear or

nonlinear model forms.

• Nonlinear CERs derived by LOLS must have standard errors

expressible ...