## Elementary Statistics (12th Edition)

a) Mean=$n\cdot p=100 \cdot 0.14=14$. Standard deviation: $\sqrt{n \cdot p \cdot (1-p)}=\sqrt{100 \cdot 0.14 \cdot 0.86}=3.47.$ b) If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=14-2\cdot3.47=7.06$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=14-2\cdot3.47=20.94$. 8 is between these two values, therefore it is not unusually low. Therefore the rate can be correct.