Answer
It means that the boy's height is $1.88$ standard deviations below the American 2-year-old boy's mean.
Work Step by Step
$z=\frac{y-\mu}{\rho}$
$-1.88=\frac{y-\mu}{\rho}$
$y-\mu=-1.88\rho$
$y=\mu-1.88\rho$
It means that the boy's height is $1.88$ standard deviations below the American 2-year-old boy's mean.
