## Elementary Statistics (12th Edition)

If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=914-2\cdot 36=842$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=914+2\cdot 36=986$. Here the maximum value is much more relevant, because that can help in designing where the overhead storage should be.