Depending on the units you had at your disposal it needed a little practice or was really easy. A bunch of marines with medics (or hydralisks) for example just kill the interceptors quickly enough so carriers aren't a threat anymore. Goliaths worked very well with their range upgrade. Psi storms work wonders and don't even need to be targeted that accurately. There are plenty of cheap and easy options against carriers but I guess as usual with such high-level threats, you shouldn't let your opponent get to the point where they can employ them or at least stay informed on what they do so you can react accordingly.