Consider that the following answer:
invlogcdf(Chi(11), log(0.975)) # 4.681885225101231 qchisq(0.975, 11) # 21.920049261021205
is wrong when comparing
invlogcdf() to the equivalent R function, but the following is correct (used as a basic check to test that whether I am using the function correctly):
invlogcdf(Normal(), log(0.975)) # 1.9599639845400534 qnorm(0.975) # 1.9599639845400536
Maybe there is an issue with how Chi-Squared inverse CDF is implemented or am I doing something wrong?