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A "miut hamatzui" is a phrased used to express a case where because of a small concern that something exists, or might happened, or does happen that the halacha is affected by this. An example is if there is a certain type of "treifah" by a kosher animal that is found in a small amount therefore this must be checked after that animal is shechted.

However what is the amount of a "miut hamatzui"? What are the different opinions in this?

(I don't feel my explanation of a "miut hamaztui" is adequate enough however it's difficult for me to express in English. Perhaps someone can edit it.)

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related judaism.stackexchange.com/a/11570/759 – Double AA Apr 11 '13 at 20:59
@DoubleAA thanks. But, makor? (aside from R' Shechter) – Yehoshua Apr 11 '13 at 21:21
@Yehoshua The generally cited mekor is the Mishk'nos Ya'akov (Vol. 1, YD § 17). – Fred Apr 11 '13 at 22:34
@Fred Sounds like an answer. However any other opinions, b'frat from earlier sources? – Yehoshua Apr 11 '13 at 22:48
It would be interesting to compare this to the pyschological studies on the same topic. – avi Dec 23 '13 at 13:27

Miut Hamatui has four opinions as brought down in the new Yalkut Yosef.

1) Rav Shelomo Zalman Aurbach who holds it is around 10%.

2) Shevet HaLevi who holds it is even less but doesn't specify.

3) Rav Bension Aba Shaul who says around 17%.

4) The opinion of the Rivash and Hacham Yishak Yosef Shelit"a who hold that it is much closer to 50% but doesn't specify.

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Welcome to Mi Yodeya. Nice answer. – Bruce James Dec 22 '13 at 19:07
Do you have the sources for all of these statements? – Yehoshua Dec 22 '13 at 19:46
I'm pretty sure Shevet Halevi (4:81, 8:180) specifically says that there is not a hard-and-fast percentage that defines the dependability of a mi'ut. – WAF Dec 23 '13 at 1:46
Are you the same person as judaism.stackexchange.com/users/1035/hacham-gabriel? If so, you may want to look into unifying this new account with the original, registered account. – Isaac Moses Dec 23 '13 at 15:50
@IsaacMoses judaism.stackexchange.com/questions/33756/… – WAF Dec 24 '13 at 3:33

Rav Eitam Henkin provides sources for all the various opinions on pages 39-62 of this kuntres.

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please summarize the points incase the link goes bad. – avi Dec 23 '13 at 15:06

Many poskim put it at 10% -- thank you Fred, Mishkenos Yaakov 1:YD17 first puts it that way. (See Rabbi JD Bleich's "Is the Milk We Drink Kosher?" in Tradition). This is the general OU opinion.

We find the figure of 10% by combining a law in Terumot -- about whether you must check that a bottle of wine in the case has spoiled before taking terumah from the batch -- with a law in Bava Basra -- about 10% being the normal spoilage rate when selling a case of wine.

The next question becomes -- 10% of what? Do I say "so long as the odds of eating a bug is <10% in this serving of lettuce, I can eat this serving"? Or perhaps we need "so long as the odds of finding a bug in this bag is <10%, I can buy this bag"? Or perhaps we even need "I can buy this case of lettuce without checking only if the odds of finding a bug anywhere in it are <10%"?

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