SOLUTION: For the 900 trading days from January 2003 through July 2006, the daily closing price of IBM stock (in$) is well modeled by a Normal model with mean $85.60 and standard deviation $

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Question 296594: For the 900 trading days from January 2003 through July 2006, the daily closing price of IBM stock (in$) is well modeled by a Normal model with mean $85.60 and standard deviation $6.20. According to this model, what is the probability that on a randomly selected day in this period the stock price closed above $91.80?
Answer by stanbon(75887) About Me  (Show Source):
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For the 900 trading days from January 2003 through July 2006, the daily closing price of IBM stock (in$) is well modeled by a Normal model with mean $85.60 and standard deviation $6.20. According to this model, what is the probability that on a randomly selected day in this period the stock price closed above $91.80?
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z(91.80) = (91.80-85.60)/6.2 = 1
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P(x > 91.80) = P(z > 1) = 0.1587
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Cheers,
Stan H.
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