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Standard Deviation

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The true length of boards cut at a mill with a listed length of 10 feet is normally distributed with a mean of 123 inches and a standard deviation of 1 inch. What proportion of the boards will be over 125 inches in length?

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Solution Summary

This solution looks at the percent of normally distributed board lengths that will be above a certain length.

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A z-score reveals how many standard deviations a value is above or below the mean. It is calculated as follows:
z-score = (value - mean)/(standard deviation)
Using the normal bell-shaped curve (standard normal distribution) one can look up what proportion of the ...

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