Answer
$6$ years
Work Step by Step
$z=\frac{y-\mu}{\rho}$
$y=\mu+z\times\rho$
Let's place some numbers: $\mu=15~years$ and $z=3$ :
- if $\rho=6~months=0.5~year$ then $y=15+3\times0.5=16.5~years$
- if $\rho=6~years$ then $y=15+3\times6=33~years$
- if $\rho=16~year$ then $y=15+3\times16=63~years$
Where $z=3$ represents teachers with the largest experience. The standard deviation of $6$ years seems to be the correct one.
