  The incomplete statistics for complex systems is characterized by a so called
incompleteness parameter $\omega$ which equals unity when information is
completely accessible to our treatment. This paper is devoted to the discussion
of the incompleteness of accessible information and of the physical
signification of $\omega$ on the basis of fractal phase space. $\omega$ is
shown to be proportional to the fractal dimension of the phase space and can be
linked to the phase volume expansion and information growth during the scale
refining process.
