I have the admission rate to a given hospital over the month of December in 2016 (114 of 550 patients were admitted = 20.727% admission rate). I also have the admission rate for the entire year of 2016 in that same hospital (1711 of 9752 patients were admitted = 17.545% admission rate). How do I ascertain whether the admission rate in December is significantly/non-significantly different than the admission rate over the entire year? I'm cautious of using the normal z-scores proportion test because the populations overlap somewhat (December 2016 vs. all of 2016). Apologies if this is particularly basic.

I'd really appreciate any guidance.
Thank you.