I plugged a USB in 500 times to test if it's three sided 

Have you ever wondered why it feels like USBs are three sided?
By repeatedly inserting a USB drive into a USB port, I'm 99.99% certain that at least 1 in 500 attemps requires 3 tries.
By analysing the data from plugging a USB in over 500 times, it's possible to derive how likely it is that a USB requires 3 tries to get it in. These results can then be used to derive lower bounds on the probability.
USB needs 3 tries at least 0.20% of the time: 99.99% confident
USB needs 3 tries at least 0.40% of the time: 99.55% confident
USB needs 3 tries at least 0.60% of the time: 96.65% confident
USB needs 3 tries at least 0.80% of the time: 88.93% confident
USB needs 3 tries at least 1.00% of the time: 76.22% confident
USB needs 3 tries at least 1.20% of the time: 60.63% confident
USB needs 3 tries at least 1.40% of the time: 44.97% confident
Disclaimer: USBs are not actually 3-sided