## Elementary Statistics: Picturing the World (6th Edition)

n $\approx$ 7
1) The z-score corresponding to an 80% Confidence level is 1.28 2) Substitute z = 1.28, $\sigma$ = 4.1 and E = 2 into the formula: n = $(\frac{z \times \sigma}{E})^{2}$ n = $(\frac{1.28 \times 4.1 }{2})^{2}$ n $\approx$ 6.885 n $\approx$ 7