In a singing contest tryout,the mean mark of the participants is 7.9 and the standard deviation is 0.64. Suppose the marks of the participants are normally distributed, and the participants with marks in the lowest 97.5% would be eliminated. For those who were selected,
a)what is the lowest standard score?
b)what is the lowest mark?
a) 2 b)9.18
pls show clear steps!thanks.
more about dispersion
2011-03-14 4:45 am
回答 (1)
2011-03-14 4:52 am
✔ 最佳答案
(a) X ~ N(7.9, 0.64^2)P(Z < (X - 7.9)/0.64) = 0.975
=> (X - 7.9)/0.64 = 1.96
So, the lowest standard score is 1.96 which becomes to 2 after round - off.
(b) The lowest mark = 2(0.64) + 7.9 = 9.18
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