## Elementary Statistics (12th Edition)

Here, n=2600 and p=0.127. a)Mean=$n\cdot p=2600 \cdot 0.127=330.2$. Standard deviation: $\sqrt{n \cdot p \cdot (1-p)}=\sqrt{2600 \cdot 0.127 \cdot 0.873}=17.$ If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=330.2-2\cdot17=296.2$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=330.2+2\cdot17=364.2$. 290 is under the lower bound therefore it is unusually low.