The highway fuel economy of a 2016 Lexus RX 350 FWD 6-cylinder 3.5-L automatic 5-speed using premium fuel is a normally distributed random variable with a mean of μ = 25.00 mpg and a standard...

The highway fuel economy of a 2016 Lexus RX 350 FWD 6-cylinder 3.5-L automatic 5-speed using premium fuel is a normally distributed random variable with a mean ofμ = 25.00mpg and a standard deviation ofσ = 1.75 mpg.


(a) What is the standard error of X⎯⎯⎯X¯ , the mean from a random sample of 16 fill-ups by one driver?(Round your answer to 4 decimal places.)


Standard error of   X⎯⎯⎯X¯             _______


(b) Within what interval would you expect the sample mean to fall, with 90 percent probability?(Round your answers to 4 decimal places.)


The interval is from _____ to _______