GeezerVison

                                                   confidence improvement accuracy (*)   (**)  (***)
fs/bench-chownSync.js n=10000 type='existing'                     0.24 %       ±2.31% ±3.09% ±4.06%
fs/bench-chownSync.js n=10000 type='non-existing'        ***     83.99 %       ±3.73% ±4.96% ±6.46%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 2 comparisons, you can thus expect the following amount of false-positive results:
  0.10 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.02 false positives, when considering a   1% risk acceptance (**, ***),
  0.00 false positives, when considering a 0.1% risk acceptance (***)