15D index score function
s(x_1,...,x_15) = v_H
Maps a respondent's levels on the 15 dimensions of the 15D, each with 5 ordinal levels, to a single index on a 0 to 1 scale, where 0 is being dead and 1 is no problems on any dimension. The index is a preference-based utility that can weight survival in QALY calculations.
15D score as an additive weighted sum of level values
v_H = sum_(j=1)^15 [I_j * w_j]