Answer:
We need at least 217 compact fluorescent light bulbs
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 M as such

In which
is the standard deviation of the population and n is the size of the sample.
How many compact fluorescent light bulbs need to be selected?
We need at least n bulbs, in which n is found when 
So







We need at least 217 compact fluorescent light bulbs
Answer:
Step-by-step explanation:
The system is almost right! The issue here is: when Sharon was adding the systems, she made a mistake. 15 + 9 = 24 not 26. From there, the rest of her steps are correct. Hope this helps!