Answer
P(X > 0) = 0.8051. This implies that ~81 out of 100 samples will have a mean monthly positive return rate.
Work Step by Step
Here we have n = 24
$σ_{x̅} = \frac{σ}{n} = \frac{0.04135 }{\sqrt 24} = 0.0084$
$z = \frac{x̅ - μ_{x̅}}{σ_{x̅}} = \frac{0 - 0.007233}{0.0084} = -0.86$
P(X > 0) = P(z > -0.86) = P(z < 0.86) = 0.8051
