Answer:
The 99% confidence interval for the true mean number of reproductions per hour for the virus is between 3.8 and 4.2.
Step-by-step explanation:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
That is z with a pvalue of
, so Z = 2.575.
Now, find the margin of error M as such

In which
is the standard deviation of the population and n is the size of the sample.

Rounding to one decimal place, 0.2.
The lower end of the interval is the sample mean subtracted by M. So it is 4 - 0.2 = 3.8 reproductions
The upper end of the interval is the sample mean added to M. So it is 4 + 0.2 = 4.2 reproductions.
The 99% confidence interval for the true mean number of reproductions per hour for the virus is between 3.8 and 4.2.