40 * 7.85 = 314
32.24 + 24.02 + 24.53 = 80.79
314 - 80.79 = 233.21
Answer is D
C - 7.6 = -4
c = -4 + 7.6
c = 3.6
Answer:
The 99% confidence interval for the true mean number of reproductions per hour for the bacteria is between 9.6 and 10.
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
.
So it is z with a pvalue of
, so 
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.

The lower end of the interval is the sample mean subtracted by M. So it is 9.8 - 0.2 = 9.6 reproductions per hour.
The upper end of the interval is the sample mean added to M. So it is 9.8 + 0.2 = 10 reproductions per hour.
The 99% confidence interval for the true mean number of reproductions per hour for the bacteria is between 9.6 and 10.