  A problem of optimal information acquisition for its use in general decision
making problems is considered. This motivates the need for developing
quantitative measures of information sources' capabilities for supplying
accurate information depending on the particular content of the latter. A
companion article developed the notion of a question difficulty functional for
questions concerning input data for a decision making problem. Here, answers
which an information source may provide in response to such questions are
considered. In particular, a real valued answer depth functional measuring the
degree of accuracy of such answers is introduced and its overall form is
derived under the assumption of isotropic knowledge structure of the
information source. Additionally, information source models that relate answer
depth to question difficulty are discussed. It turns out to be possible to
introduce a notion of an information source capacity as the highest value of
the answer depth the source is capable of providing.
