What are the chances of this Metronome situation happening?

Question

So I beat Maylene in Platinum, then went straight to the double battle with Dawn VS the two Team Galactic Grunts. I sent out my Houndoom, Dawn her Clefairy. While the enemy Zubat were Wing Attack-ing, Dawn used Gravity and I used Thunder Fang, but it didn’t OHKO. I killed one Zubat so Dawn started using Metronome, and landed a Sheer Cold on the other. The Grunts then sent out Stunky and Croagunk. I switched into Togetic while Dawn used Sing on the Croagunk. Then, using Metronome, my Togetic used and landed a Fissure on the Stunky!

I was surprised by this because a) both moves would have been super effective had they been regular damaging moves and b) I’m guessing hitting two automatic OHKO moves in a row is very unlikely considering their tendency to miss. So what are the chances of this happening?

Comments

@KRLW890 Where did you find that out? This site says it only fails if the target is 30+ levels above the user.

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@♪Barbara Bingbong♪™ this site mentions wrong formula. You can check the correct here at Bulbapedia:
https://bulbapedia.bulbagarden.net/wiki/Fissure_(move)

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Gen 1 & 2:

Acc =  ( user_level - target_level ) * 2/256 + 76/256 ) * 100%

Gen 3 & above:

Acc = ( user_level - target_level + 30 ) * 1%

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Hmm, well I have had problems with this copy before (like Gardenia’s Roserade somehow being immune to Prinplup’s Peck) so I don’t know whether my brother did something funky to it when he owned it (probably). If you still want to answer, just imagine the being immune thing doesn’t exist, or use the gen 2 equation. Anything that works and still gets a rough answer since there’s no way I can find out what the heck my gamecard is thinking...

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Ah! I misremembered, it wasn’t Dawn’s Clefairy that used Fissure, I switched to my Togetic - level 28 (planning on ditching it) and it used Metronome. I’ll edit.

Answer 1

In Gen 4, there are 442 moves that Metronome can call, so there was a 1/442 chance of getting Sheer Cold, and then the same chance of getting Fissure after that. We could change this to a 3/442 chance for the first and a 4/442 chance for the second to count the other OHKO moves that could have been pulled here for the same outcome (only 3 for the first because Fissure doesn’t affect Zubat), but you pointed out how both moves would have been super effective if they were regular attacking moves, so I’m going to keep them as a 1/442 chance, each.

OHKO moves use a unique accuracy formula that is unaffected by accuracy and evasion modifiers (including Gravity). The formula is (user_level - target_level + 30) * 1%. Dawn’s Clefairy was level 25 and used Sheer Cold against a level 24 Zubat, giving it an accuracy of 31%. Your Togetic was level 28 and used Fissure against a level 26 Stunky, giving it an accuracy of 32%.

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Here’s our final equation:
1/442 * 31/100 * 1/442 * 32/100 = 62/30,525,625, which is approximately 1/492,349, or a 0.0002031080445% chance.

Comments

Isn't it (User Level - Target Level + 30) * 100%?

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Whoops, yes. I used that formula while calculating, but I guess I didn’t write it correctly :P

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O_O ...Okay then...

Thanks!