The mean of response variable is $$f(x, \bold{\theta}) = \frac{1}{(1 + \exp(-b (x - a)))},$$ where \(\bold{\theta} = (a, b)\).
FIM_logistic(x, w, param)vector of design points. In IRT, \(x\) is the person ability parameter.
vector of design weight. Its length must be equal to the length of x and sum(w) should be 1.
vector of model parameters \(\bold{\theta} = (a, b)\). In IRT parameter \(a\) is the item difficulty parameter and parameter \(b\) is the item discrimination parameter.
Fisher information matrix.
There is no closed-form for the locally optimal design.
For minimax and standardized D-optimal design, the optimal design is symmetric around point
\((a^L + a^U)/2\) where \(a^L\) and \(a^U\) are the
lower bound and upper bound for parameter \(a\), respectively. In mica,
options sym and sym_point in control can be used to make the search
for the optimal design easier.
Other FIM: FIM_comp_inhibition,
FIM_emax_3par, FIM_exp_2par,
FIM_exp_3par,
FIM_logisitic_1par,
FIM_logistic_4par,
FIM_loglin, FIM_michaelis,
FIM_mixed_inhibition,
FIM_noncomp_inhibition,
FIM_power_logistic,
FIM_uncomp_inhibition