Pretty good, but could be better.
It's not bad. Remember that the actual yield is the physical experiment conducted, different than the theoretical yield, calculations done as a pre-lab.
Thus, the better you are to 100% accuracy, the better. 91.5% is pretty good, but you can do better. Best results should be 95% and higher. Anything lower than 80% is bad, and you should redo the lab.
Inaccuracy can also be evident in the calculations so make sure that all calculations are done correctly and accurately.
Hope this helps :)