## Elementary Statistics: Picturing the World (6th Edition)

a) $x$ = 1852.5 days b) $x$ = 1531.63 days
PART A i) The z-score that corresponds to 80% is 0.84 ii) Solve $z = \frac{x-\mu}{\sigma}$ for $x$ using $\sigma$ =212.5 and $\mu$ = 1674: $z = \frac{x-\mu}{\sigma}$ $x$ = $\mu$ + $z\sigma$ $x$ = 1674 + (0.84 x 212.5) $x$ = 1852.5 days PART B i) The z-score that corresponds to 25% is -0.67 ii) Solve $z = \frac{x-\mu}{\sigma}$ for $x$ using $\sigma$ =212.5 and $\mu$ = 1674: $z = \frac{x-\mu}{\sigma}$ $x$ = $\mu$ + $z\sigma$ $x$ = 1674 + (-0.67 x 212.5) $x$ = 1531.63 days