## Elementary Statistics (12th Edition)

If a value is unusual, then it is more than two standard deviations far from the mean. (Mean=5 and standard deviation=1.6 from the previous exercise) $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=5-2\cdot1.6=1.8$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=5+2\cdot1.6=8.2$. 1<1.8, therefore it is an unusually low number.