Answer
$P(p̂ \geq 0.255) = 0.0031$. Hence it will be unusual as the probability < 0.05.
Work Step by Step
To calculate $P(p̂ \geq 0.255)$, we need to find the z-score:
$z = \frac{p̂ - μ_{p̂}}{σ_{p̂}}$
$= \frac{.255-.310}{0.02}$ = -2.74
$P(z \geq -2.74) = 0.0031$, hence:
$P(p̂ \geq 0.255) = 0.0031$ (unusual)
