ughly 
\chi^2 with one degree of freedom if the n-th order correction is a good
model for the data. 
 Thus, one only moves to the n+1-th order correction of q is relatively
large.  The chance that 
one moves from the n-th to the n+1-th order correction when the n-th
order correction 
(eg. a type 1 error) is sufficient is given by the Prob(\chi^2_1 >
threshold).  The constructor 
of this class allows you to directly set this tolerance (in terms of
probability that the n+1-th
 term is added unnecessa