You can't actually say what the rate is, but you can say there's a such-and-such chance it is within a certain range of the number you came up with. This is the confidence interval on a proportion. So if you had 2263 crits in 10000 swings and wanted a 95% confidence interval, you could say there your margin of error is 1.96 * sqrt(.2263*0.7737/10000) + 0.5/10000 = 0.00825133679 (a 95% chance that the rate is between 21.80% and 23.46%).

I'm saying this because the number of swings is but one factor here--the closer the observed rate is to 50%, the more swings you'd need to establish the same margin of error.

Edit: whoa, it's a kenji sighting