SOLUTION: Daily profits at a retail store have an average of $1000. If at least 88.9% of values are between $800 and $1200, what is the standard deviation of daily profits

Question 1071080: Daily profits at a retail store have an average of $1000. If at least 88.9% of values are between $800 and $1200, what is the standard deviation of daily profits
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Daily profits at a retail store have an average of $1000. If at least 88.9% of values are between $800 and $1200, what is the standard deviation of daily profits
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That 88.9% of area is centered at the mean.
88.9/2 = 44.45% of the area is to the left of the mean.
The boundary z-value = invNorm(0.5-0.4445) = -1.5937
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Solve for "s"::
800 = -1.5937*s + 1000
Ans:: s = 125.5
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Cheers,
Stan H.
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