Answer
n $\approx$ 25
Work Step by Step
1) The z-score corresponding to a 95% Confidence level is 1.96
2) Substitute z = 1.96, $\sigma$ = 2.5 and E = 1 into the formula:
n = $(\frac{z \times \sigma}{E})^{2}$
n = $(\frac{1.96 \times 2.5 }{1})^{2}$
n $\approx$ 24.01
n $\approx$ 25
