## Elementary Statistics (12th Edition)

If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=67.3-2\cdot10.3=46.7$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=67.3+2\cdot10.3=87.9$. Here, $45<46.7$, therefore the value is unusual, because it is smaller than the minimum usual value mean.