Symbol c_fa

Its job in the formula

$c_f$a is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Where the article explains it

Where $c_{fa}$ is the fitness cost of a false alarm and $c_{miss}$ is the fitness cost of a miss, the threshold that minimizes total expected fitness cost is to infer H whenever: $\frac{P(D \mid H)}{P(D \mid \lnot H)}$ \; > \; $\frac{P(\lnot H)}{P(H)}$ $\cdot$ $\frac{c_{fa}}{c_{miss}}$ When the two error costs are equal, the cost ratio on the right collapses to one, and the rule reduces to the ordinary Bayesian classifier that a norm blind to consequences would prescribe — the classical, “unbiased” threshold heuristics-and-biases research uses as its comparison point.

Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →