Nestor R. answered • 08/03/19

Professional experienced using mathematics and statistics

The null hypothesis H_{0} = p = 0.05. The alternative is not specified so assume H_{1} = p ^= 0.05 (two-sided test)

When alpha = 0.01 z_{.005 }= 2.575

25/400 = 0.625

calculate Z = (0.0625 - 0.05) / sqrt((0.0625*0.9375)/400)

=0.0125/0.0121= 1.0328

Z < z_{0.005} so H_{0} cannot be rejected and the marketing director's claim has validity.