Refer to Exercise 9.2.2. In each case (n = 100 and n = 400) construct a 95%

Question:

Refer to Exercise 9.2.2. In each case (n = 100 and n = 400) construct a 95% confidence interval for the population proportion of mutants.
Exercise 9.2.2
In an experiment with a certain mutation in the fruit fly Drosophila, n individuals were examined; of these, 20% were found to be mutants. Determine the standard error of if
(a) n = 100 (20 mutants).
(b) n = 400 (80 mutants).