the mean is 5.8the variance is 2.4We have to find the standard deviation and round it to one decimal place.

To calculate the standard deviation given the variance, we just take the square root.
That because the variance is:
[tex]v=\sigma^2[/tex]And the standard deviation is:
[tex]\sigma[/tex]So, calculating the standard deviation:
[tex]\sigma=\sqrt[]{\sigma^2}=\sqrt[]{v}=\sqrt[]{2.4}=1.54919\ldots\approx1.5[/tex]Thus, the standard deviation is 1.5.