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I'm not sure why you're using a z-test when you can calculate the probability directly. The chance of landing 22 or fewer Hurricanes out of 46, given that the true probability of landing one is 0.7, is approximately 0.00136, or 0.136%. You're off by a bit more than a factor of two...
But if you Snatch a Shell Break, Cloyster will still be dead on the next turn, except you have a massive boost.
That being said, it's still highly situational to be virtually ineffective.
I can see it being useful if you know you're faster than a sweeper who has accumulated, say, two Swords Dances, and you need a guaranteed revenge kill.
You might also want to give the expected BP by weighting the damage with the probabilities.
It's just under 85 for non-skill link, for those interested.
Sturdy only prevents 1HKO moves such as Fissure or Sheer Cold. It doesn't do anything to any other move that would kill in one hit, such as Earthquake.
All right, so this is a bit random, but is anyone else reeeeeally turned off by Victini's cold, lifeless eyes? It's not even cute. I find it threatening/eerie.
Eh, many Pokemon counteract Breloom very effectively. Two Pokemon off the top of my head that I can think of (and are also fairly common) that completely stop it are Gengar and Celebi.