Answer:
We have been given confidence interval 95%, mean 20 , data set 30 and standard deviation 3.
We will use the formula:
Here,
Z-score value at 95% confidence interval is 1.96
On substituting the values in the formula to plug the values:
Now, we have a formula for marginal error:
Marginal error means your answer will be within that percentage only.
Say you have 3% marginal means your value will be within 3% real population 95% of the time.