Answer:
197
Explanation:
Sample proportion is; p^ = 12/50 = 0.24
Margin of error of 5% is given by the formula;
ME = (z_0.05) √[p^(1 - p^)/n]
Let's make n(number of sample) the subject.
n = ((z_0.05)/ME)²((p^)(1 - p^))
From tables, the z-score of 0.05 is 1.645
Thus;
n = ((1.645)/0.05)²(0.24(1 - 0.24))
n ≈ 197