Calling the floor to replace a misdealt turn card?

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the idea is that the 7 has the same chance to come on the river as any other card.

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The 7 of spades has a better chance of coming than any other card. Assume a 10 player game, there are are 46 unknown cards on the river so a random card has a 1/46 chance of coming. Since the 7 of spades is known to be in the stub it has a 1/25 chance of coming on the river. In Omaha it has a 1/5 chance of coming on the river (in a 10 handed game).