In a certain town, the judge is suspected of unfair jury selection. The population in the area is 80% ethnic Hmong, yet on average he only has two Hmong on a 12-member jury. Assuming fair selection, what is the expected number of Hmong, and what is the variance?

- stapel_eliz
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The probability that any particular person is from the Hmong tribe is p = 0.8; the number of "trials" is n = 12. The formula for the expected mean (in this case, the expected number of Hmong) is np. You should get an answer of "between nine and ten" being Hmong.In a certain town, the judge is suspected of unfair jury selection. The population in the area is 80% ethnic Hmong, yet on average he only has two Hmong on a 12-member jury. Assuming fair selection, what is the expected number of Hmong, and what is the variance?

The formula for the variance, given probability p and a number of trials n, is np(1 - p). In this case, p = 0.8 and n = 12.

Yeah, the guy seems "guilty as charged".

i get 9.6 and 1.92 thnx