math-normal distribution
2012-01-12 10:48 pm
A set of concrete cubes with the random strengh variable X~N(39,42),find the probability of strength X between 30mPa and 42mPa.
回答 (1)
2012-01-13 5:40 am
✔ 最佳答案
Answer: 0.595824Pr (30 <= X <= 42)
= Pr( (30 - 39)/√42 < Z < (42 - 39)/√42 )
= Pr( -1.3887 < Z < 0.46291 )
= 0.595824
So, the probability of strength X between 30mPa and 42mPa is 0.595824
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https://hk.answers.yahoo.com/question/index?qid=20120112000051KK00384