The numbers in the table below represent the annual return in $\%$ earned on shares held in a particular company for the $8$ successive years. Considering these returns as a sample of returns on the shares, calculate the sample mean return and the sample standard deviation of the returns. Round your answer to $4$ decimal places, if necessary.

$4\mathrm{.}5$

$8$

$8\mathrm{.}6$

$2\mathrm{.}3$

$0\mathrm{.}5$

$2\mathrm{.}8$

$4$

$8\mathrm{.}3$