Step-by-step explanation:

Answer: let's say x = 1
16 x 1 =16
16+20=36
36x1/2=18
Step-by-step explanation:
Answer:
its impossible without getting a negative number
Step-by-step explanation:
Answer:
The sample size required is at least 171
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.
What sample size is required?
A samle size of at least n is required, in which n is found when 
So






Rouding up
The sample size required is at least 171