a) Find sample mean and test statistics ¯ x = 405+378+411 3 = 398 z = ¯ x-μ σ √ n = 398-354 33 √ 3 =2.3094 b) p-value=P(Z>2.3094)=1-φ(2.3094) = 0.0104 Shaded area represents the p-value. c) Yes. The result is statistically significant at α =0.05 level. We reject H0 and there is evidence of increased sales. 1
