Unbiased sample standard deviation of one to five

Treat the values $1,2,3,4,5$ as an i.i.d. sample and estimate the population standard deviation with the usual sample formula (using $n-1$). What do you get?

$\sqrt{5/2}\approx1.58$. The mean is $3$ and the squared deviations sum to $4+1+0+1+4=10$; dividing by $n-1=4$ gives $2.5$, whose square root is about $1.581$.