The fuel economy of a 2011 Lexus RX 350 2WD 6 cylinder 3.5 L automatic 5-speed using premium fuel is a normally distributed random variable with a mean of μ = 25.0 MPG - and a standard deviation of σ = 1.25 MPG.
(a) What is the standard error of X-bar, the mean from a random sample of 16 fill-ups by one driver?
(b) Within what interval would you expect the sample mean to fall, with 90 percent probability?