Chapter 8 - Section 8.1 - Assess Your Understanding - Applying the Concepts - Page 411: 23d

P(X > 0) = 0.8531. This implies that 85 out of 100 samples will have mean positive rate of return for a 36 month period.

Here we have n = 36 $σ_{x̅} = \frac{σ}{n} = \frac{0.04135 }{\sqrt 36} = 0.0011$ $z = \frac{x̅ - μ_{x̅}}{σ_{x̅}} = \frac{0 - 0.007233}{0.0011} = -1.05$ P(X > 0) = P(z > -1.05) = P(z < 1.05) = 0.8531