Elementary Statistics: Picturing the World (6th Edition)

Reject $H_{o}$ at α = 0.05
$z = \frac{x̄ - μ}{σ/\sqrt n}$ $z = \frac{39.2-40}{1.97/\sqrt 5}$ $= \frac{-0.8}{0.394}$ = -2.03 P(z < -2.03 or z > 2.03) = 0.0424 < α Hence reject $H_{o}$ at α = 0.05