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Standard Deviation

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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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 ...

Solution Summary

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