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Figure 2 | BMC Medical Research Methodology

Figure 2

From: Optimizing cost-efficiency in mean exposure assessment - cost functions reconsidered

Figure 2

Principally different cases of local extremes of the one-variable objective variance function. The boundaries of possible resource investment, i.e. the choice set, are given by n i = 1 and n i = n i,max . In I1, the variance function has a local minimum at n i = n i *; this is an interior optimal solution with minimal variance. For I2, the variance function also has an interior zero derivative, at n i = n i °, but this solution maximizes the variance and is therefore not useful. In cases E1 and E2, the local extreme of the variance function lies below and above the choice set, respectively. In these cases, minimal variance is obtained at the lower (E1) and upper (E2) choice set boundary.

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