Answer:
The minimum sample size required for the estimate is 345.
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 = 1.96.
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 standard deviation is known to be 1.8.
This means that
What is the minimum sample size required for the estimate?
This is n for which M = 0.19. So
Rounding up to the next integer:
The minimum sample size required for the estimate is 345.