SOLUTION: A popular retail store knows that the purchase amounts by its customers is a random variable that follows a normal distribution with a mean of $30 and a standard deviation of $9.

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Question 976643: A popular retail store knows that the purchase amounts by its customers is a random variable that follows a normal distribution with a mean of $30 and a standard deviation of $9.
What are the two dollar amounts, equidistant from the mean of $30, such that 90% of all customer purchases are between these values?
Answer by FrankM(1040) About Me  (Show Source):
You can put this solution on YOUR website!
I want to find the z score that equated to 45%.
Z=1.64
1.64*9 = $14.76
90% of purchases are between $15.24 and $44.76