Draws the density and cumulative
distribution curves for the specified non-central t distribution.
(This distribution is not in Excel.) The parameter δ is given by
δ = −L′ √n,
with L′=(L−μ) ⁄σ
and AQL = Φ(L′). Constant k is calculated.
If the following impossible values are given:
AQL = 0, AQL is computed from L;
α = 0, k is not calculated.
The parameters 'tol' and 'maxit' relate to the NAG procedure
G01GBF (see the manual). For establishing the values of this type of parameters
(which is typically not easy), only trial and error is suggested here.
† or (mainly Amer. English)
"noncentral". | 
