% of catching a Raid boss?

My level4 raid boss catching history:
vs Tyranitar. Twice. Caught 0.
vs Lapras. Once. Caught 1. Iv below 82%

I caught this yesteday. I used pinap on first try and it immediately jumped out. I then used a golden razz and he proceeded to dodge 4 great throws in a row. On my second to last premier ball i caught it.
Golden razz are to the left not right so swipe left.

It really just depends on your throwing ability and of course a hefty dose of luck. Just as with any wild pokemon, it's important to throw curveballs and use razzberries or golden razzberries as well as to hit the smallest circle possible. Beyond that, it's just up to luck whether or not you actually get the catch. Doing more damage and holding the gym before the raid begins give you more balls to increase the chance of catching with one of them. I've also confirmed that it is possible to get a critical catch on a raid boss.

I caught all the Level 1 - 3 raid bosses that I have encountered. Using only razz berries.

The one level 4 boss I fought was a tyranitar but I couldn't catch it. Too hard without golden razz berries.

I caught all of my level 4 raids, usually by about the 4th - 5th ball, 1 Charzard, 1 Snorlax, 2 Tyranitars. Used golden razzberry on the last 2 I caught, as I wasn't aware of them before and they don't show on my berry screen without scrolling over. IVs have all been in the 80's.

Used golden berries and got multiple great throws with spin. couldn't catch it, was a tyranitar.