In this thesis, Signal Detection Theory (SDT) is extended to two dimensions of signal. Two modes of signal occurrence are considered:
1) Two kinds of signal occur simultaneously.
2) Each signal occurs separately with different signal occurrence probabilities.
Cost functions are developed including false alarm and missing error costs, and optimal decision criterions are obtained by minimizing total expected cost.
An experiment was performed to evaluate inspector's task behavior in the simulated inspection task of an item having two kinds of fault. From hit and false alarm frequencies data, subjects' performances concerned with two types of fault detection were analyzed.