be careful, define your words, if by choking you mean unable to talk or breathe then you may be correct, but only for an infant or small child.
if it is a child of a few years old, then the Heimlich maneuver should be done first.
if by choking you mean a fit of coughing, then you should not do back blows.
back blows are somewhat controversial in any case, and there are other ways of dealing with a child who is unable to breathe.
if you want to give medical advice, take a cpr course. This goes for the poster you are correcting as well