## Elementary Statistics (12th Edition)

Mean: $0\cdot0.674+1\cdot0.28+2\cdot0.044+3\cdot0.003+4\cdot0=0.38$. Standard deviation: $\sqrt{(0-0.38)^2\cdot0.674+(1-0.38)^2 \cdot0.28+(2-0.38)^2\cdot0.044+(3-0.38)^2\cdot0.003+(4-0.38)^2\cdot0}=0.58.$. If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=0.38-2\cdot0.58=-0.78$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=0.38+2\cdot0.58=1.56.$. 3 is more than the upper bound, therefore it is unusually high.