The combined city/highway fuel economy of a 2016 Toyota 4Runner 2WD 6-cylinder 4-L automatic 5-speed using regular gas is a normally distributed random variable with a range 17 mpg to 22 mpg.

Estimate the standard deviation using Method 3 (the Empirical Rule for a normal distribution) from Table 8.8. (Round your answer to 4 decimal places.)

What sample size is needed to estimate the mean with 90 percent confidence and an error of 0.25 mpg? (Enter your answer as a whole number. Use a z-value taken to three decimal places in your calculations.)

The combined cityr'highway fuel economy of a 2016 Toyota 4Runner 2WD 6cylinder 4L automatic 5speed using regular gas is a normally distributed random variable with a range 17 mpg to 22 mpg. la] Estimate the standard deviation using Method 3 [the Empirical Rule fora normal distribution] from Table 8.8. {Round your answer to 4 decimal places.) standamueviaon lb} What sample size is needed to estimate the mean with 90 percent condence and an error of i 0.25 mpg? {Enter your answer as a whole number. Use a z-value taken to three decimal places in your calculations.}