  We study the scaling of the magnetic susceptibility in the square Ising model
based upon the delta-expansion in the high temperature phase. The
susceptibility chi is expressed in terms of the mass M and expanded in powers
of 1/M. The dilation around M=0 by the delta expansion and the parametric
extension of the ratio of derivatives of chi, chi^{(ell+1)}/chi^{(ell)} is used
as a test function for the estimation of the critical exponent gamma with no
bias from information of the critical temperature. Estimation is done with the
help of the principle of minimum sensitivity and detailed analysis revealed
that ell=0,1 cases provide us accurate estimation results. Critical exponent of
the sub-leading scaling term is also estimated.
