The Basic Difference Between an Arbitrary and a Conventional Sample

The basic difference between an arbitrary and a conventional sample size determination is that:

A) the conventional approach has no defensible logic,whereas the arbitrary approach appears to have faulty logic.
B) the conventional approach doesn't appear to be logical,whereas the arbitrary approach has defensible logic.
C) the arbitrary approach has no defensible logic,whereas the conventional approach is logical.
D) the arbitrary approach has no defensible logic,whereas the conventional approach appears logical but is faulty.
E) the arbitrary approach,though arbitrary,has sound logic,and the conventional approach has conventional support.